Object tracking apparatus, object tracking system, object tracking method, display control device, object detection device, and computer-readable medium

ABSTRACT

An object tracking apparatus, method and computer-readable medium for detecting an object from output information of sensors, tracking the object on a basis of a plurality of detection results, generating tracking information of the object represented in a common coordinate system, outputting the tracking information, and detecting the object on a basis of the tracking information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims priority from Japanese PatentApplication No. 2014-196176, filed on Sep. 26, 2014, and Japanese PatentApplication No. 2014-224050, filed on Nov. 4, 2014. The entiredisclosures of the above-referenced applications are incorporated hereinby reference in their entirety.

BACKGROUND

1. Technical Field

The present disclosure may generally relate to object trackingapparatuses, object tracking systems, object tracking methods, displaycontrol devices, object detection devices, programs, andcomputer-readable media.

2. Description of the Related Art

In recent years, systems in which plural cameras and the like are usedfor tracking an object (e.g., a person) have been developed. An exampleof an object tracking system may include a plurality of tracking devicesembedded in a camera, with each of the tracking devices tracking theobject in a distributed fashion. For example, the plurality of trackingdevices embedded in the camera may co-operate with one another intracking the object. Another example may be a method for tracking thesame object captured by a plurality of capturing devices on the basis ofthe respective tracking results of individual capturing devices.

Another example in a related art may be a method for excluding an objectthat does not need tracking.

Another example in a related technique may be an apparatus that detectsa moving object in an image captured by one capturing device.

In some embodiments, in the case of the related technology, there may bea possibility that the tracking accuracy for tracking an object (e.g., amoving object) in an image captured by a camera located at a farposition from the object becomes degraded. For example, with the relatedtechnology, the tracking accuracy of the camera may make it difficult tointegrate the tracking results of the object. Moreover, even if thesystem can integrate the tracking results, the accuracy for detectingthe location of the object may become degraded.

SUMMARY OF THE DISCLOSURE

Exemplary embodiments of the present disclosure may overcomedisadvantages of prior systems. However, the exemplary embodiments arenot required to overcome the specific disadvantages, and the exemplaryembodiments of the present disclosure may provide other advantages.

According to an aspect of the present disclosure, an object trackingapparatus is disclosed. The object tracking apparatus may include amemory storing instructions, and at least one processor configured toprocess the instructions to generate a first detection result of anobject from output information of a first sensor, generate a seconddetection result of the object from output information of a secondsensor, generate first tracking information of the object based on acombination of the first and second detection results, wherein the firsttracking information is represented in a common coordinate system thatis associated with the first and the second sensor, and track the objectbased on the first tracking information.

According to another aspect of the present disclosure, an objecttracking system including sensors and an object tracking apparatus isdisclosed. The object tracking apparatus may include a memory storinginstructions and at least one processor configured to process theinstructions to generate a first detection result of an object fromoutput information of a first sensor, generate a second detection resultof the object from output information of a second sensor, generate firsttracking information of the object based on a combination of the firstand second detection results, wherein the first tracking information isrepresented in a common coordinate system that is associated with thefirst and the second sensor, and track the object based on the firsttracking information.

According to another aspect of the present disclosure, an objecttracking method is disclosed. The tracking method may be performed by atleast one processor. The method may include generating a first detectionresult of an object from output information of a first sensor,generating a second detection result of the object from outputinformation of a second sensor, generating first tracking information ofthe object based on a combination of the first and second detectionresults, wherein the first tracking information is represented in acommon coordinate system that is associated with the first and thesecond sensor, and tracking the object based on the first trackinginformation.

According to another aspect of the present disclosure, an objectdetection apparatus is disclosed. The object detection apparatus mayinclude a memory storing instructions and at least one processorconfigured to process the instructions to detect an object from outputinformation of sensors on a basis of tracking information represented ina common coordinate system, and wherein the tracking informationindicating tracking result of the object tracked on a basis of aplurality of detection results output from individuals of a plurality ofobject detection devices.

According to another aspect of the present disclosure, a non-transitorycomputer-readable storage medium that stores instructions is provided.The instructions, when executed by a computer, may enable the computerto implement a method. The method may include generating a firstdetection result of an object from output information of a first sensor,generating a second detection result of the object from outputinformation of a second sensor, generating first tracking information ofthe object based on a combination of the first and second detectionresults, wherein the first tracking information is represented in acommon coordinate system that is associated with the first and thesecond sensor, and tracking the object based on the first trackinginformation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an example of an object trackingapparatus according to embodiments of the present disclosure;

FIG. 2 is a diagram illustrating an example of an object tracking systemaccording to embodiments of the present disclosure;

FIG. 3 is a diagram describing an example of an association betweentargets and trackers according to embodiments of the present disclosure;

FIG. 4 is a block diagram illustrating an example of a detection unit ofan object tracking apparatus according to embodiments of the presentdisclosure;

FIG. 5 is a block diagram illustrating an example of an object detectionunit of an object tracking apparatus according to embodiments of thepresent disclosure;

FIG. 6 is a block diagram illustrating an example of an integraltracking unit of an object tracking apparatus according to embodimentsof the present disclosure;

FIG. 7 is a diagram describing an example of object sequential trackingprocessing performed by an example of an object tracking apparatusaccording to embodiments of the present disclosure;

FIG. 8 is a flowchart illustrating an example of an object trackingmethod according to embodiments of the present disclosure;

FIG. 9 is a block diagram illustrating an example of an object trackingapparatus according to embodiments of the present disclosure;

FIG. 10 is a block diagram illustrating an example of a detection unitof an object tracking apparatus according to embodiments of the presentdisclosure;

FIG. 11 is a schematic diagram illustrating an example of an applicationof an object tracking apparatus according to embodiments of the presentdisclosure;

FIG. 12 is a schematic diagram illustrating an example of an applicationof an object tracking apparatus according to embodiments of the presentdisclosure;

FIG. 13 is a schematic diagram illustrating an example of an applicationof an object tracking apparatus according to embodiments of the presentdisclosure;

FIG. 14 is a schematic diagram illustrating an example of an applicationof an object tracking apparatus according to embodiments of the presentdisclosure;

FIG. 15 is a block diagram illustrating an example of a detection unitof an object tracking apparatus according to embodiments of the presentdisclosure;

FIG. 16 is a block diagram illustrating an example of an objectdetection unit of the detection unit of an object tracking apparatusaccording to embodiments of the present disclosure;

FIG. 17 is a block diagram illustrating an example of an integraltracking unit of an object tracking apparatus according to embodimentsof the present disclosure;

FIG. 18 is a diagram describing an example of an object batch trackingprocessing performed by an example of an object tracking apparatusaccording to embodiments of the present disclosure; and

FIG. 19 is a block diagram illustrating an example of a hardwareconfiguration of a computer (information processing apparatus) capableof providing embodiments of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the disclosedembodiments. It will be apparent, however, that one or more embodimentsmay be practiced without these specific details. In other instances,well-known structures and devices are schematically illustrated in orderto simplify the drawings.

First Example

A first example of the present disclosure will be described in detailwith reference to the drawings. With reference to FIG. 2, an objecttracking system (also referred to as a system) will be described. FIG. 2is a diagram illustrating an example of an object tracking systemaccording to embodiments of the present disclosure. As illustrated inFIG. 2, object tracking system 1 may include an object trackingapparatus 10, the plurality of cameras (20-1 to 20-N (N may be a naturalnumber)), and one display device 30 or more. In this example, theplurality of cameras (20-1 to 20-N) may be referred to as cameras 20.

The object tracking apparatus 10, the cameras 20, and the display device30 may be coupled communicatively with one another via a network 40. Insome embodiments, the display device is not included in the objecttracking system 1. In some embodiments, the display device 30 may bedirectly coupled with the object tracking apparatus 10 without beingcoupled via the network 40.

At least some of cameras 20 may include a sensor for detecting anobject. In some embodiments, the cameras 20 may be used as sensors fordetecting an object. In other aspects, sensors are not limited tocameras. The sensors may be any devices capable of position measurementsuch as radio sensors. In some embodiments, a combination of a pluralityof sensors such as an integrated combination of a radio sensor and acamera may be used. The object tracking apparatus 10 may obtain visualinformation such as color information by using the cameras 20 as asensor.

In this example, the following descriptions will be made under theassumption that information captured by a sensor includes informationrelated to a video captured by at least one of cameras 20. In someembodiments, if a sensor is a radio sensor, information captured by thesensor may include information related to a radio wave captured by theradio sensor.

The object tracking apparatus 10 may be an apparatus for trackingobjects in videos captured by individuals of the plurality of cameras20. The functional configuration of the object tracking apparatus 10will be described below with reference to other drawings.

The display device 30 may display tracking results of objects obtainedby the object tracking apparatus 10. The display device 30 may be adevice that displays a video captured by at least one of the cameras 20.The display device 30 may be a device that displays trajectoryinformation and the like.

(Object Tracking Apparatus 10)

An example of object tracking apparatus 10 will be described as follows.FIG. 1 is a block diagram illustrating an example of the functionalconfiguration of an object tracking apparatus (e.g., object trackingapparatus 10 of FIG. 2) according to embodiments of the presentdisclosure. As illustrated in FIG. 1, the object tracking apparatus 10may include a plurality of detection units (100-1 to 100-N) and anintegral tracking unit 200. In this example, the plurality of detectionunits (100-1 to 100-N) may be referred to collectively as detectionunits 100.

(Detection Unit 100)

The detection units 100 may detect an object using output informationfrom the cameras 20 on the basis of tracking information that is outputfrom the integral tracking unit 200 as described below and that isrelated to the object on a frame before the target frame from which theobject is to be detected. In this example, the output information fromthe cameras 20 may include information related to video data captured bythe cameras 20.

In this example, it is assumed that individuals of the plurality ofdetection units 100 and individuals of the plurality of cameras 20 areassociated on a one-to-one basis. For example, the detection unit 100-1may detect objects from a video captured by the camera 20-1, and thedetection unit 100-2 may detect objects from a video captured by thecamera 20-2. But embodiments of the present disclosure are not limitedto such an association. For example, the detection unit 100-1 may detectobjects from a video captured by the camera 20-N, where N is any numberother than 1.

In some embodiments, individuals of the plurality of detection units 100and individuals of the plurality of cameras 20 is not associated on aone-to-one basis. For example, the detection unit 100-1 may detectobjects from videos captured by, for example, cameras 20-1 and 20-2.

The operation of a detection unit 100 will be described as follows. Adetection unit 100 may receive video data captured by a correspondingcamera 20 (hereinafter, the video data may be referred to as a “cameravideo”). For example, as shown in FIG. 1, video data captured by acamera 20-n (wherein n may represent any of 1 to N) may be denoted as acamera video (n). The camera video may be a video that is captured, inreal time, by one of cameras 20 (e.g., a surveillance camera). Thecamera video may also be a video that was captured earlier by one of thecameras 20, stored in a memory unit or the like, and is then decoded (orreproduced) afterward. The video data may include time informationindicating time at which the video is captured.

The detection unit 100 may receive tracking information related to theobject on the previous frame from the integral tracking unit 200. Theprevious frame may be a frame just before a target frame from which theobject is to be detected (the current frame). The previous frame mayalso be a frame that is located a predetermined number of frames beforethe current frame. Tracking information on one previous frame ortracking information on a plurality of previous frames may be used fordetecting the object. In a case where the detection unit 100 performsdetection of an object on the first frame, the detection unit 100 doesnot receive the tracking information related to the object (or does notuse tracking information related to the object), because there is notracking information related to the object on the previous frame.

The detection unit 100 may perform detection of the object from thereceived camera video using the camera video and tracking informationrelated to the object on the previous frame. The detection performed bythe detection unit 100 will be referred to as object detection. Asdescribed above, in the case where the object detection is performed onthe first frame, the detection unit 100 may perform the object detectionwithout using the tracking information related to an object on theprevious frame. For the following disclosure, a detected object will bereferred to as a “target,” and each target is associated with a targetregion. For example, in a case where a target is an object, the targetregion can include a region bounded by a boundary of the object. In someembodiments, the detection result of an object (also referred to as an“object detection result” or a “detection result” hereinafter) maybecome a set of targets.

An object detection result may include information for each target, forexample, information indicating the position of the target, the size ofthe target, and the like. In some embodiments, the object detectionresult may include, for example, information indicating a rectanglecircumscribing a region in a frame of a video from which each target isdetected, the coordinate values of the centroid of the target region,information indicating the width of each target, information indicatingthe height of each target, and the like. In some embodiments, the objectdetection result may include other information. For example, the objectdetection result may include the coordinate values of the uppermost endand the lowermost end of the target region instead of or in addition tothe coordinate values of the centroid of the target region. The objectdetection result may also include information for each target such asinformation indicating the position and size of each target.

For the following disclosure, descriptions will be made based on anexample in which an object detection result includes the coordinatevalues of the lowermost end of each target and information indicating arectangular circumscribing each target. In some instances, thecoordinate values of the lowermost end of the target may coincide withthe coordinate values of a point at which the object contacts a floor(e.g., the ground) and/or the coordinate values of the midpoint of thelower side of a rectangular circumscribing the object. In someinstances, if the object is a person, the coordinate values of thetarget may be the coordinate values of the position of his/her feet.

In some embodiments, the detection unit 100 may transform the coordinatevalues included in the object detection result into coordinate values ina common coordinate system defined for a space to be captured by acombination of the plurality of cameras 20 (hereinafter referred to as“capturing space”). The transformed coordinate values can then beprovided as part of the object detection result.

An object detection result may also include information indicating theshape of each target in addition to the above-described information. Insome embodiments, the object detection result may include silhouette (orcontour) information indicating a target boundary that defines thetarget region, and the like. The silhouette information may includeinformation that distinguishes pixels inside the target region andpixels outside the target region. For example, the silhouetteinformation may be image information that sets the values of the pixelsinside the target region to 255 and the values of the pixels outside thetarget region to 0. For example, the silhouette information may beinformation indicating values obtained by extracting shape descriptors(shape features), which are standardized in MPEG-7, from the silhouetteshape. In some embodiments, an object detection result may also includethe appearance features of an object. For example, the object detectionresult may include the features related to the color, pattern, shape,and the like of the object.

In some embodiment, an object detection result may include informationindicating a likelihood that represents the accuracy (e.g., to indicatethe reliability) of the detection of an object (hereinafter referred toas “target likelihood information”). The target likelihood informationmay include information for calculating the likelihood of correctlydetecting the object. In some embodiments, the target likelihoodinformation may include information related to the predicted accuracy ofobject detection such as the score value at the time of objectdetection, the distance of the detected object from the camera, the sizeof the detected object, and the like. In some instances, the detectionunit 100 may calculate the likelihood of detecting the object itself,and set the calculated target likelihood to the likelihood indicated bythe target likelihood information.

The detection unit 100 may output the target detection result to theintegral tracking unit 200.

(Integral Tracking Unit 200)

The integral tracking unit 200 may receive detection results output fromthe respective detection units 100. The integral tracking unit 200 maytrack an object on the basis of the respective detection results. Insome instances, the integral tracking unit 200 may track one or moreobjects, or perform object tracking by using an object detection resultrelated to the one or more objects, which are detected by the detectionunits 100 from videos captured by the respective cameras 20, with eachof the cameras 20 being associated with a corresponding detection unit100. In some embodiments, the integral tracking unit 200 may generateone or more tracking results of the respective object(s) (objecttracking results) represented in the common coordinate system. Asdescribed above, the integral tracking unit 200 may integrate objectdetection results detected by the respective detection units 100 fromvideos captured by the respective cameras 20, with each of the cameras20 being associated with a corresponding detection unit 100. In someembodiments, object tracking performed by the integral tracking unit 200may be referred to as object integral tracking.

Information generated for each object as an object tracking result maybe referred to hereinafter as a tracker. In some embodiments, a trackermay include information indicating the position of a tracked object,information related to the motion model of the object, and the like, asinformation related to the tracked object (or as an object trackingresult). In some embodiments, information included in the tracker is notlimited to the above-described information. Because the position of atracked object can occur at a time before the current time, the trackermay include information about the past positions of the object.

In some embodiments, object tracking may be regarded as processing inwhich, by associating a target detected by object detection with atracker generated before the detection of the detected target, objectsin respective frames can then be associated with each other. The objecttracking will be described with reference to FIG. 3. FIG. 3 is a diagramdescribing an example of processing in which targets and trackers areassociated by the integral tracking unit 200. As illustrated in FIG. 3,it is assumed that the number of targets is M and the number of trackersis K (M and K may be integers equal to 0 or larger). The integraltracking unit 200 may associate individuals of these M targets withindividuals of these K trackers. When the integral tracking unit 200associates a target with a tracker, the integral tracking unit 200 maypredict a current position of an object with reference to the pastposition of the object indicated by information included in the tracker,and associate the target with the tracker using an index indicating therelation between the target and the tracker.

In some instances, the integral tracking unit 200 may predict theposition of the object on the current frame on the basis of the positionof the object detected on the previous frame and the motion model of theobject calculated and stored for each tracker. The prediction mayinvolve applying a Kalman filter, a particle filter, etc.

For example, the integral tracking unit 200 may associate an objecttracking result (tracker) on the previous frame with an object includedin the detection result (target) based on at least some of the followingfactors:

(1) a distance (e.g., degree of closeness) between the position of theobject on the current frame predicted using the tracker and the positionof the target;

(2) a relationship (e.g., similarity) between an appearance feature ofthe target and that of the object whose tracking result is indicated bythe tracker;

(3) the likelihood of detecting the object and the likelihood oftracking the object (a likelihood of a tracker).

In some embodiments, it may be possible to make the associationprocessing reduce to a cost minimization problem in a bipartite graph asillustrated in FIG. 3. In some embodiments, the integral tracking unit200 may solve above-described problem using an algorithm such as theHungarian method.

In FIG. 3, an example of a case where some targets and respectivetrackers are associated each other is illustrated by arrows. Forexample, the uppermost target may be associated with the uppermosttracker.

In some embodiments, if there is a target that is not associated withany tracker, the integral tracking unit 200 may determine whether thetarget can be regarded as a newly appeared object or not. If theintegral tracking unit 200 determines there is a high possibility thatthe target has newly appeared, the integral tracking unit 200 maygenerate a new tracker related to the target. For example, in FIG. 3, itis assumed that a target with a symbol m (referred to as a target mhereinafter) is a target that is not associated with any tracker. Inthis case, the integral tracking unit 200 may determine whether thetarget m can be regarded as a newly appeared object or not, and if thetarget m can be regarded so, the integral tracking unit 200 may generatea new tracker related to the target m.

In some embodiments, if there is a tracker that is not associated withany target, the integral tracking unit 200 may determine whether or notthe tracker indicates information related to an object that hasdisappeared from the capturing space. If there is a high possibilitythat the tracker indicates information related to an object that hasdisappeared from the capturing space, the integral tracking unit 200 maydelete the tracker. For example, in FIG. 3, it is assumed that a trackerwith a symbol k (referred to as a tracker k hereinafter) is a trackerthat is not associated with any target. In this case, the integraltracking unit 200 may determine whether the tracker k indicatesinformation related to a disappeared object or not, and if the tracker kindicates information related to the disappeared object, the integraltracking unit 200 may delete the tracker k.

The integral tracking unit 200 may continue to perform object trackingby repeating the above-described processes on a frame-by-frame basis. Insome embodiments, the integral tracking unit 200 may associate anidentifier (e.g., a unique ID) with each tracker related to videoscaptured by the cameras 20, and manage each tracker (and the associatedtracking result) using the corresponding identifier. In someembodiments, the integral tracking unit 200 may include a value obtainedby evaluating the reliability of a tracking result (hereinafter,referred to as a “likelihood of a tracker”) into the tracker as aparameter of the tracker. In some embodiments, the newest position of atracked object among positions indicated by information that is includedin the corresponding tracker and that represents the positions of thetracked object will be referred to hereinafter as “the position of thetracker.” The size of the object at the newest position will be referredto hereinafter as “the size of the tracker.”

The integral tracking unit 200 may update information indicating theposition of each tracker, the likelihood of each tracker, and the likeon the basis of the result of the association processing. Informationrelated to the position of a tracker may be information represented in acommon coordinate system defined in a capturing space captured by theplurality of cameras 20. The information represented in the commoncoordinate system may include information related to coordinate valuesin the common coordinate system. The coordinate values in the commoncoordinate system may be, for example, coordinate values indicating theposition on a floor. A coordinate system associated with each of cameras20 may be referred to as the “individual coordinate system” of one ofcameras 20. The individual coordinate system may be a coordinate systemon an image captured by one of cameras 20. Hereinafter, the followingdescriptions will be made based on information related to positionsrepresented as coordinate values in the common coordinate system, andbased on information related to positions represented as coordinatevalues in the individual coordinate system of at least some of cameras20.

The integral tracking unit 200 may generate a tracker whose informationis updated on the basis of the result of the association processing as anew object tracking result. The integral tracking unit 200 may output,for example, information indicating the position and/or size of thetracker, information indicating the likelihood of the tracker, and thelike as tracking information.

The tracking information may include the coordinate values of eachtracker in the common coordinate system as information indicating theposition of each tracker. The tracking information may be fed back tothe detection units 100. In some embodiments, the detection units 100may receive the tracking information, and use the tracking informationfor detecting objects on the following frames.

The integral tracking unit 200 may be configured so as to output theobject tracking result including both above-described trackinginformation and other information included in the tracker to thedetection units 100.

As described above, the object tracking apparatus 10 according toembodiments of the present disclosure may perform object tracking byintegrating object detection results based on videos captured byindividuals of the plurality of cameras 20. The object trackingapparatus 10 may provide the obtained tracking information for objectdetection on the following frame.

As described above, the object tracking apparatus 10 may detect objectsfrom videos using the tracking result related to a previous frame. Forexample, if there is an object whose video data is not captured by afirst camera 20 but is captured by a second camera 20, the objecttracking apparatus 10 may use the tracking result of the above-describedobject for object detection related to a video captured by the firstcamera 20. In such a manner, when the above-described object laterappears in an area whose video data is captured by the first camera 20,the associated detection unit 100 can detect the above-described object.As a result, the object tracking apparatus 10 can perform objecttracking related to the above-described object.

The object tracking apparatus 10 can improve the accuracy of objectdetection in comparison with a case where the tracking result related tothe previous frame is not used. Because the object tracking apparatus 10performs object tracking using the detection results from a plurality ofdetection units, the accuracy of the tracking result obtained as a wholemay also be improved.

(Detail of Detection Unit 100)

The functions of the respective units of the object tracking apparatus10 will be described in more detail with reference to FIGS. 4 to 8. FIG.4 is a block diagram illustrating an example of a detection unit 100 ofthe object tracking apparatus 10 according to embodiments of the presentdisclosure. As illustrated in FIG. 4, the detection unit 100 may includean object detection unit 110, a common coordinate transformation unit(hereinafter referred to as “second transformation unit”) 120, and anindividual coordinate transformation unit (hereinafter referred to as“first transformation unit”) 130. In FIG. 4, a camera video (n) (n canbe any integer from 1 to N) that the detection unit 100 receives, asshown in FIG. 1, is denoted as a camera video.

The individual coordinate transformation unit 130 may receive trackinginformation output from the integrated tracking unit 200. The individualcoordinate transformation unit 130 may transform the coordinate valuesof each tracker in the common coordinate system into coordinate valueswithin a frame captured by the corresponding camera 20 (e.g., thecoordinate values represented in an individual coordinate systemassociated with the corresponding camera 20). When it is assumed that acoordinate values in the common coordinate system is (X, Y, Z), and acoordinate values in the individual coordinate system of the camera 20is (x, y), the individual coordinate transformation unit 130 maycalculate the coordinate values (x, y) in the individual coordinatesystem of the corresponding camera 20 associated with the detection unit100 that includes the individual coordinate transformation unit 130 fromthe coordinate values of a tracker (X, Y, Z) in the common coordinatesystem. In this case, the individual coordinate transformation unit 130may obtain at least camera parameters that represent the cameraposition, the camera posture, and the like of the corresponding camera20 associated with the detection unit 100 by performing calibration. Insome embodiments, the individual coordinate transformation unit 130 maytransform the coordinate values in the common coordinate system intocoordinate values in the individual coordinate system of the camera 20using the obtained camera parameters.

In some embodiments, the camera parameters may be stored in a memoryunit in the detection unit 100. In other aspects, the camera parametersmay be stored in a memory region in the individual coordinatetransformation unit 130. In the latter case, the individual coordinatetransformation unit 130 may be configured so as to provide the cameraparameters to the common coordinate transformation unit 120.

For example, it is assumed that an object is a person, and informationindicating the position of the corresponding tracker includesinformation indicating the coordinate values of the foot position of theperson and the coordinate values of the top position of the head of theperson. It is assumed that the coordinate values of the foot positionare (X0, Y0, 0) and the coordinate values of the top position of thehead are (X0, Y0, H) (H may be the height of the person). It is assumedthat a camera 20 that is associated with a detection unit 100, whichincludes an individual coordinate transformation unit 130, is the camera20-1.

In this case, the individual coordinate transformation unit 130 maycalculate the foot position (x0, y0) and the top position of the head(x1, y1) on a frame captured by the camera 20-1 using camera parametersrelated to the camera 20-1. If the information indicating the positionof the tracker includes information indicating a circumscribingrectangle, the common coordinate transformation unit 120 as describedbelow may already have calculated the value representing the width ofthe circumscribing rectangle by transforming the value representing thewidth of the circumscribing rectangle into a value of the width in thecommon coordinate system using the camera parameters. In this case, theindividual coordinate transformation unit 130 may use a value that isobtained by transforming again the value of the width in the commoncoordinate system into that in the individual coordinate system by usingthe above-described camera parameters as the width of the circumscribingrectangle.

In some cases, one camera 20 cannot capture the video data of all of theobjects associated with each of the trackers, and there may be a casewhere one or more objects are outside the field of view of the onecamera 20. In some embodiments, if information indicating the positionof a tracker included in tracking information includes informationrelated to an object that is outside the field of view of a camera 20associated with a detection unit 100, the corresponding individualcoordinate transformation unit 130 does not calculate the coordinatevalues of the object in the individual coordinate system of theabove-described camera 20. In this case, the individual coordinatetransformation unit 130 may exclude the coordinate values of a trackerassociated with an object that is not viewable (e.g., outside the fieldof view) of the camera 20 from transformation from the common coordinatesystem into the individual coordinate system. In some embodiments, theindividual coordinate transformation unit 130 may register an area ofcoordinate values in the common coordinate system, which is within thefield of view by each camera 20, in advance in a memory unit or the likefor each camera 20, and determine whether each object is located withinthe area that reflects field of view of each camera or not. In otheraspects, the individual coordinate transformation unit 130 may actuallytransform the coordinate values of an object in the common coordinatesystem into a coordinate values in the individual coordinate system, andwhen the transformed coordinate values indicates a location outside aregion monitored by a camera 20 associated with the detection unit 100,or a coordinate values in the relevant individual coordinate systemcannot be obtained, the individual coordinate transformation unit 130may determine that the object whose coordinate values is transformed isnot within the field of view of the camera 20.

The individual coordinate transformation unit 130 may output the resultobtained by transforming the coordinate values of trackers, which areincluded in tracking information output from the integral tracking unit200, in the common coordinate system (e.g., tracking information) intothe coordinate values in the individual coordinate system of the camera20 associated with the detection unit 100. In some embodiments, theindividual coordinate transformation unit 130 may transform trackinginformation represented in the common coordinate system into trackinginformation represented in the individual coordinate system, and outputthe transformed tracking information to the object detection unit 110.Hereinafter, the phrase denoted by “coordinate values of the individualcoordinate system” may represent coordinate values of the individualcoordinate system of a camera 20 which is associated with a detectionunit 100.

The object detection unit 110 may receive a camera video from the camera20 associated with the detection unit 100 including the object detectionunit 110. The object detection unit 110 may receive the trackinginformation, which is transformed into the information indicating thecoordinate values in the individual coordinate system, from theindividual coordinate transformation unit 130. The object detection unit110 may detect objects from the received camera video on the basis ofthe above-described tracking information.

In some embodiments, the object detection unit 110 may generate adetection result. The object detection unit 110 may output the generateddetection result to the common coordinate transformation unit 120. Insome embodiments, the detection result may be a detection resultrepresented in the individual coordinate system.

The configuration of the object detection unit 110 will be described inmore detail with reference to FIG. 5. FIG. 5 is a block diagramillustrating an example of object detection unit 110 according toembodiments of the present disclosure. As illustrated in FIG. 5, theobject detection unit 110 may include a recognition-type objectdetection unit (a first object detection unit) 111 and a searching areasetting unit 112.

The searching area setting unit 112 may receive the trackinginformation, which is transformed into the coordinate values in theindividual coordinate system, from the individual coordinatetransformation unit 130. The searching area setting unit 112 may obtainan area (e.g., a searching area) within which an object on the currentframe is searched, using the tracking information transformed into thecoordinate values in the individual coordinate system. In someembodiments, the searching area setting unit 112 may predict theposition of the object on the current frame on the basis of trackinginformation including the corresponding tracking result related to theprevious frame. The searching area setting unit 112 may obtain asearching area within which the object is searched for using thepredicted position. In some embodiments, the searching area may also bereferred to as an object detection area.

In some embodiments, the tracking information that the searching areasetting unit 112 receives may be information related to a trackingresult of the object on the past frame viewed from the time of a frameon which processing is currently to be performed. In some embodiments,the tracking result of the object on the past frame may also be referredto as the past tracking result of the object. The searching area settingunit 112 may predict the motions of each object, and predict thepositions of each object on the current frame. The predicted position ofan object will be referred to as predicted position. The searching areasetting unit 112 may set the vicinity of the predicted position to thesearching area for the object.

The searching area setting unit 112 may predict the motion of eachobject using the motion model of the corresponding object calculatedfrom the past tracking result. For example, if the position of an objecthas not changed among the tracking results of the past several frames(at least the past two frames), the searching area setting unit 112 maydetermine that the object is standing still, and regard the position ofthe object obtained from the tracking result of the object as thepredicted position. For example, if tracking results of past severalframes indicate that an object is moving, the searching area settingunit 112 may assume that the object is moving at a constant velocity,and calculate the predicted position in consideration of timedifferences between the current time and the times of the past frames.

The tracking results related to the past several frames used by thesearching area setting unit 112 when the searching area setting unit 112predicts the motion of each object may be included in the trackinginformation. The motion model of each object obtained from the trackingresults related to the past several frames may be included in theabove-described tracking information.

In some embodiments, the predicted position may be included in thetracking information. The integral tracking unit 200 may include thevalue which is obtained using a Kalman filter or a particle filterduring performing the object tracking into the tracking information asthe predicted position.

In some cases, there may be a possibility that a new object appears inthe peripheral part of the area which can be captured by a camera 20,within the field of view of the camera 20. Moreover, in a case where thesite which a camera 20 captures includes a doorway or the like, theremay be a possibility that a new object appears in the field of view ofthe camera 20. The searching area setting unit 112 may include suchareas (the peripheral of the frame and/or the doorway) on the frameincluded in a video captured by the camera 20 into the relevant objectsearching areas.

The searching area setting unit 112 may output information indicatingthe set object searching area (searching area information) to therecognition-type object detection unit 111.

The recognition-type object detection unit 111 may receive the searchingarea information from the searching area setting unit 112. Therecognition-type object detection unit 111 may detect an object from acamera video input on the basis of the received searching areainformation. The recognition-type object detection unit 111 maytemporarily store the frame of the input camera video in a memorysection such as a buffer therein. The recognition-type object detectionunit 111 may receive the searching area information, and perform objectdetection processing using the searching area information. In someinstances, the recognition-type object detection unit 111 may performobject detection within an area indicated by the searching areainformation (within the searching area) using a discriminator that hasbeen made to learn the image features of the object.

For example, if an object is a person, the recognition-type objectdetection unit 111 may perform the detection of the person using adiscriminator that has been made to learn the characteristic areas of aperson (for example, the head area or upper body of the person). Forexample, the recognition-type object detection unit 111 may use adiscriminator that has been made to learn the entirety of a person asthe above-described discriminator. The recognition-type object detectionunit 111 may use various types of discriminators as the discriminator.For example, the recognition-type object detection unit 111 may use adiscriminator that has been made to learn the images of the head area,upper body, entire body, and the like of a person by means of a CNN(convolutional neural network). For example, the recognition-type objectdetection unit 111 may perform feature extraction such as HOG (Histogramof Oriented Gradients) feature extraction, and use a discriminator suchas SVM (support vector machine) or GLVQ (generalized learning vectorquantization). In some instances, the recognition-type object detectionunit 111 may use various existing recognition-based detection techniquesother than the above-described techniques.

As described above, the recognition-type object detection unit 111according to the present example may detect an object within a searchingarea set by the searching area setting unit 112. In some embodiments,the recognition-type object detection unit 111 may perform objectdetection within a searching area that the searching area setting unit112 narrows down using the tracking result on the previous frame.Because the recognition-type object detection unit 111 may avoidperforming object detection within an area where there is littlepossibility that the object exists, superfluous erroneous detection maybe prevented from being performed. Further, the recognition-type objectdetection unit 111 can speed up object detection processing.

The searching area within which the recognition-type object detectionunit 111 performs object detection may include not only an areaindicated by searching area information but also an area determined bysilhouette information calculated by using background subtractionprocessing. In some embodiments, the recognition-type object detectionunit 111 may use a common area of an area determined by silhouetteinformation and an area indicated by object searching area informationas an area within which object detection is performed (e.g., a searchingarea).

The recognition-type object detection unit 111 may generate a result ofperforming the object detection (a detection result), and output thedetection result to the common coordinate transformation unit 120. Insome embodiments, the coordinate values of the object included in thedetection result may include coordinate values in the individualcoordinate system.

With reference to FIG. 4, the common coordinate transformation unit 120of the detection unit 100 will be described. The common coordinatetransformation unit 120 may receive the object detection resultrepresented in the individual coordinate system from the objectdetection unit 110. The common coordinate transformation unit 120 maytransform the coordinate values in the individual coordinate systemincluded in the received detection result into coordinate values in thecommon coordinate system. As described above, the common coordinatetransformation unit 120 can generate information for integrating thedetected positions of objects related to the respective cameras 20.

In some embodiments, the common coordinate transformation unit 120 maytransform the coordinate values in the individual coordinate systemincluded in the object detection result into coordinate values in thecommon coordinate system using the camera parameters of the camera 20which is associated with the detection unit 100 including the commoncoordinate transformation unit 120. For example, if the coordinatevalues of the lowermost end of an object on a frame captured by thecamera 20 are (x0, y0), the common coordinate transformation unit 120may transform the coordinate values into coordinate values (X0, Y0, 0)in the common coordinate system. Because it is assumed that the groundis a plane with Z=0, a Z-axis component of the transformed coordinatevalues may become 0. It is assumed that the coordinate values of theuppermost end of the object is (x1, y1) and that the height of theobject is H, and that the uppermost end of the object is just above thelowermost end of the object (in the vertical direction). In this case,the common coordinate transformation unit 120 may transform thecoordinate values of the uppermost end of the object (x1, y1) intocoordinate values in the common coordinate system (X0, Y0, H). Thecommon coordinate transformation unit 120 may calculate the height ofthe object by searching for H that satisfies the transformationcondition as described above. As described above, the common coordinatetransformation unit 120 may calculate coordinate values (X, Y, Z) in thecommon coordinate system for each of detected objects.

If H has been already known, the common coordinate transformation unit120 may use the already-known value as it is.

The common coordinate transformation unit 120 may output the detectionresult including transformed coordinate values (coordinate values in thecommon coordinate system) to the integral tracking unit 200. In someembodiments, the common coordinate transformation unit 120 may outputthe detection result represented in the common coordinate system to theintegral tracking unit 200. The common coordinate transformation unit120 may include the silhouette information and information about theappearance features (color, pattern, shape, etc.) and the like into eachof one or more objects included in the detection result as informationrelated to the each object. The common coordinate transformation unit120 may output the detection result including the above-describedinformation to the integral tracking unit 200.

(Detail of Integral Tracking Unit 200)

The functional configuration of the integral tracking unit 200 will bedescribed in more detail with reference to FIG. 6. FIG. 6 is a blockdiagram illustrating an example of integral tracking unit 200 of theobject tracking apparatus 10 according to embodiments of the presentdisclosure. As illustrated in FIG. 6, the integral tracking unit 200 mayinclude a prediction unit 210, a memory unit 220, an association unit230, and an update unit 240. Because the integral tracking unit 200 maysequentially track videos from each of the cameras 20 on acamera-by-camera basis, the integral tracking unit 200 may also bereferred to as a sequential tracking unit.

An example of sequential object tracking (also referred to as objectsequential tracking or sequential integral tracking) performed by theintegral tracking unit 200 will be described with reference to FIG. 7.FIG. 7 is a diagram for describing an object sequential trackingprocessing performed by the integral tracking unit 200 according toembodiments of the present disclosure. FIG. 7 may be an exampleillustrating timing at which each of a camera A, a camera B, and acamera C (of the plurality of cameras 20) obtains an image in a casewhere the number of cameras is three. In FIG. 7, each of horizontal axesis a time axis; the righter a time point is located along the time axis,the later time the time point indicates. As illustrated in FIG. 7, it isassumed that the camera A obtains images at the time t1, t5, and t8.Similarly, it is assumed that the camera B obtains images at the timet2, t4, t6, and t9, and it is assumed that the camera C obtains imagesat the time t3, and t7.

As illustrated in FIG. 7, the times at which frames (images) areobtained by respective cameras 20 (time stamps) do not always coincideacross all the cameras 20, and it may be typical that they do notcoincide. In some cases, frame intervals may be different from onecamera 20 to another. A camera 20 can capture frames between non-uniformframe intervals.

The detection unit 100 may perform detection in a chronological orderrelated to camera videos, which are output asynchronously from thesecameras 20, and output detection results to the integral tracking unit200.

The integral tracking unit 200 according to the present example mayperform sequential tracking processing on images in the order ofoccurrences of the images. In some embodiments, in FIG. 7, the integraltracking unit 200 may perform integration of the object detectionresults of the respective cameras using an object detection resultrelated to an image captured at the time t1 by the camera A, and performobject tracking. The integral tracking unit 200 may perform integrationof the object detection results of the respective cameras using objectdetection results related to images captured at the times t2 by thecamera B, t3 by the camera C, t4 by the camera B, and so on in thisorder, and perform object tracking. In a case where not all objects arewithin the field of view of all of the cameras 20, the integral trackingunit 200 may perform object tracking on objects that are viewable toeach camera 20 with high possibilities.

With reference to FIG. 6, the respective units of the integral trackingunit 200 will be described.

The memory unit 220 may store information related to trackers that areassociated with objects (targets) included in the detection resultsreceived by the integral tracking unit 200. The information related totrackers stored in the memory unit 220 may be managed by the update unit240 using the trackers' IDs. The information related to trackers mayinclude information related to objects, tracking results related to theobjects being included in the trackers, information related toparameters including the likelihoods of the trackers, and the like. Insome embodiments, the information related to the trackers according tothe present disclosure is not limited to the above. The informationabout the objects may include information indicating the past positionsof the objects, information related to the motion models of the objects,and the like. In some embodiments, the information about the objectsaccording to the present disclosure is not limited to the above. Theinformation about the objects may include information included in theabove-described object detection results.

The following descriptions will be made based on an example of theintegral tracking unit 200 in which the memory unit 220 is embedded. Insome embodiments, the memory unit 200 according to the presentdisclosure is not limited to the above. The memory unit 220 may beinstalled not in the integral tacking unit 200, but be installed in theobject tracking apparatus 10 independently of the memory unit 220. Inother aspects, the memory unit 220 may be realized by separate memorydevices or the like other than the object tracking apparatus 10.

If the memory unit 220 is not embedded in the integral tacking unit 200,the memory unit 220 may be configured to store data and the like used inthe object tracking apparatus 10. For example, the memory unit 220 maystore camera videos captured by the cameras 20, camera parameters forthe respective cameras 20, areas of coordinate values in the commoncoordinate system that are viewable to respective cameras 20, and thelike.

The prediction unit 210 may predict the positions of objects on thecurrent frame with reference to the memory unit 220. In someembodiments, the prediction unit 210 may predict the current positionsof the objects on the basis of the motion models of the objects usingthe tracking results of the objects (trackers) on the previous frame.Information indicating the positions of the objects may be representedin the common coordinate system.

The motion models of the objects, which are used for estimating thepositions by the prediction unit 210, may be motion models stored in thememory unit 220, or may be motion models calculated by the predictionunit 210 before the prediction unit 210 predicts the positions of theobjects.

For the prediction of the positions of the objects performed by theprediction unit 210, prediction processing such as Kalman filterprocessing or particle filter processing may be applicable. In someembodiments, the prediction unit 210 may calculate the velocities of theobjects from the several tracking results in past, predict movementamounts from the positions on the previous frame using the velocitiesunder the assumption that the objects move at constant velocities, andpredict the current positions by adding the movement amounts to thepositions on the previous frame.

The prediction unit 210 may output the prediction results to theassociation unit 230.

The association unit 230 may receive detection results output fromrespective detection units 100. In FIG. 6, the detection result (n) (nmay represent any of 1 to N) may represent a detection result outputfrom the corresponding detection unit 100-n. The association unit 230may receive the prediction results from the prediction unit 210. Theassociation unit 230 may associate targets included in the detectionresults with trackers using the above-described prediction results withreference to the memory unit 220.

The association unit 230 may search for the combinations of the targetsand the trackers that improve the accuracy of the entirety of theassociation processing. The likelihood that a target m and a tracker kis associated with each other may be the product of Pm, ηk, and qkm,where Pm is the likelihood of the target m, ηk is the likelihood of thetracker k, and qkm is the likelihood that represents the possibilitythat the target m and the tracker k is the same object. The associationunit 230 may calculate the likelihood for correctly associating eachpair of a target and a tracker, and search for the combinations of thetargets and the trackers that improve the total accuracy of all thecombinations.

The likelihood of a target may be a value representing reliability(e.g., accuracy) of object detection. An accuracy of object detectionmay depend on the size of an object of detection target (referred to asa detection object) on a screen (e.g., on a frame), a distance from acamera 20 to the detected position of the object, the appearance of theobject from the camera 20, and the like.

For example, in the case where a detection object is so small that thesize of the detection object can be detected by a narrow margin, theaccuracy of the objection detection may become lower. For example, inthe case where the size of a detection object deviates from the apparentsize of the object that can be assumed from camera parameters, theaccuracy of the objection detection may become lower. For example, ifthe detected position of an object is far from a camera 20 or if anillumination condition for an area within which the object exists is badand it is therefore difficult to detect the object, the accuracy of theobjection detection may become lower. For example, if appearanceindicated by data used for learning of a discriminator is different fromactual appearance of the object (for example, viewing angles of bothcases are different from each other), the accuracy of the objectiondetection may become lower.

The association unit 230 may calculate the likelihood of a target inconsideration of the above-described characteristics (conditions). Insome embodiments, the association unit 230 may calculate the likelihoodof the target using the target likelihood information included in thedetection results received from the detection units 100. In a case wherethe detection units 100 calculate the likelihood of the target andincludes the calculated likelihood into the detection results as thetarget likelihood information, the association unit 230 may use thelikelihood included in the target likelihood information as it is. Insome cases, in the calculation of the likelihood of the target, onlysome of the above-described items (conditions) are taken intoconsideration.

The likelihood of a tracker may be a value representing reliability(e.g., accuracy) of object tracking. An accuracy of object tracking mayvary depending on the tracking result of object tracking on the previousframe. For example, in the tracking results for frames (e.g., pastframes) before the current frame, a tracker that is associated with thecorresponding target may have a high accuracy of object tracking. Forexample, a tracker that is not associated with the corresponding targetmay have a low accuracy of object tracking. Therefore, the associationunit 230 may vary a likelihood on the basis of the result whether atarget and a tracker have been associated with or not on each frame. Insome embodiments, if the target and the tracker are associated with eachother, the association unit 230 may increase the likelihood of thetracker, and if the target and the tracker are not associated with eachother, the association unit 230 may decrease the likelihood of thetracker.

In some embodiments, if the position of the tracker is far from a camera20, an error of the position of the tracker may increase. As a result,it may become difficult that such a tracker is associated with an objectincluded in the detection results (e.g., a target). Therefore, theassociation unit 230 may vary a ratio, with which the likelihood of atracker varies, in accordance with a distance between the position ofthe tracker and the camera 20. In some embodiments, the association unit230 may vary a ratio, with which the likelihood of a tracker varies, inaccordance with an angle formed by a horizontal plane including a camera20 and the direction of the gaze to which an object whose trackingresult is indicated by a tracker is viewed from the camera 20 (e.g., adepression angle or an elevation angle).

For example, in a case where an object whose tracking result isindicated by a tracker (hereinafter, referred to as a tracker's object)is near to a camera 20, and a depression angle of the camera 20 to theobject is larger than a predetermined angle, the accuracy of theposition of the object may be high. Therefore, the tracker and thetarget can be easily associated with each other. In this case, theassociation unit 230 may increase the ratio.

If a tracker's object is far from a camera 20, and a depression angle ofthe camera 20 to the object is smaller than a predetermined angle, thesize of the object on a frame captured by the camera 20 may becomesmall. Further, a little deviation on an image may become a largedeviation in a real space. Therefore, there may be a high possibilitythat the accuracy of the detected position of this object becomes low.In this case, the association unit 230 may decrease the ratio. Asdescribed above, the association unit 230 may calculate the likelihoodof a tracker.

As described above, because the association unit 230 can reflect adetection result obtained by a camera 20 nearer to a tracker's object inthe likelihood of the tracker, the accuracy of tracking can be improvedas a whole. In some cases, in the calculation of the likelihood of thetracker, only some of the above-described items are taken intoconsideration.

A likelihood qkm that represents the identity of a target m and atracker k may represent a probability that both target m and tracker kare the same as each other. In the case where an object represented by atarget and an object represented by a tracker's object are the same,there is a high possibility that the position of the target and theposition of the tracker's object is near to each other. Therefore, theassociation unit 230 may vary the likelihood in accordance with thedistance between a target and a tracker's object. In some embodiments,if the distance between the target m and the tracker's object is small,the association unit 230 may set the value of the likelihood qkm largerand if the distance is large, the association unit 230 may set the valueof the likelihood qkm smaller.

In this case, if the target m is far from the camera 20, or if thedepression angle of the camera 20 to the target m is smaller than apredetermined angle, there may be a high possibility that the detectionaccuracy of the position of the target m becomes low. Therefore, theassociation unit 230 may calculate the distance between a target and atracker's object using, for example, a Mahalanobis distance which iscalculated with an error (e.g., to reflect ambiguity) of the detectedposition of the target taken into consideration, rather than using asimple Euclidean distance. In some embodiments, the association unit 230may adopt a method, in which the degree of change of the likelihood qkmis controlled in accordance with the distance in consideration of theambiguity, instead of the above-described methods. In some embodiments,if the above ambiguity is large, the association unit 230 may set thechange of the likelihood qkm smaller in accordance with the distancebetween the target m and the tracker's object. As described above, theassociation unit 230 can alleviate an adverse effect given to theassociation processing by the deviation of the position of a target.

The association unit 230 may take similarities in the appearances of atarget and a tracker into consideration. In some embodiments, theassociation unit 230 may extract the features of the colors, patterns,and shapes of the target and the tracker's object in advance, andcalculate the likelihood qkm by evaluating these similarities.

For example, the association unit 230 may calculate color histograms ofthe object for both the target and the tracker's object, evaluatesimilarity in these color histograms using the overlapped portion of thecolor histograms, and calculate the likelihood qkm in consideration ofthe similarity. As is the case with the likelihood ηk of the tracker andthe likelihood Pm of the target, in some cases, in the calculation ofthe likelihood qkm that represents the identity of a target and atracker, only some of the above-described items are taken intoconsideration.

The association unit 230 may calculate the above likelihoods taking intoconsideration the cases where the object gets outside the field of viewof the camera 20, or the object cannot be detected because it is hiddenby another object. As described above, even in a case where an object isnot detected, or in a case where the object is outside the field angleof the camera 20, the integral tracking unit 200 can track the objectwith high accuracy.

As described above, a problem in which respective likelihoods arecalculated and the associations of targets and trackers that make therespective likelihoods maximum as a whole are searched for can reduce toan allocation problem that makes a cost minimum by converting each ofthe likelihoods to a cost with a monotonically non-increasing function(e.g., a problem about which target should be associated with whichtracker). This allocation problem can be efficiently solved using amethod such as the Hungarian method, for example.

The association unit 230 may output the result of the associationprocessing to the update unit 240. The result of the associationprocessing may include information indicating the association between atarget and a tracker, and the above-described respective likelihoodsincluding at least information related to the likelihoods of trackers.

In the present example, the association unit 230 may have performedassociation processing using both likelihoods of targets and likelihoodsof trackers. In some embodiments, the association unit 230 may performassociation processing using the likelihoods of either targets ortrackers.

The update unit 240 may update information related to trackers. Theupdate unit 240 may generate these trackers as a new object trackingresult. In some embodiments, the update unit 240 may receive the resultof the association processing from the association unit 230. The updateunit 240 may calculate the current position of the tracker's object onthe basis of the result of the association processing. The update unit240 may update the information related to trackers stored in the memoryunit 220. Updated information may include, for example, informationrelated to parameters such as the position and/or size of the objectwhose tracking information is included in the tracker, the motion modelof the object, and the likelihood of the tracker. In the presentdisclosure, updated information may not be limited to the above. Theupdate unit 240 may update the updated information among informationstored in the memory unit 220.

The calculation of the current position of a tracker's object performedby the update unit 240 will be described. The update unit 240 maycalculate the current position of the tracker's object taking theaccuracy of the position of the corresponding target into consideration.For example, it is assumed that the update unit 240 calculates thecurrent position of the tracker's object by weighing the predictedposition of the object, which is predicted by the update unit 240 usingthe tracker, and the detected position of the target associated with thetracker. In this case, the update unit 240 may control the weights inaccordance with the accuracy of the position of the target.

For example, if the target is far from a camera 20, and the depressionangle of the camera 20 to the target is small, there may be apossibility that the accuracy of determining the position of this targetis low. In such a case, the update unit 240 may set the weight for theposition of the target smaller.

For example, if the target is near to the camera 20, and the depressionangle of the camera 20 to the target is large, it may be expected thatthe accuracy of determining the position of this target is high. In sucha case, the update unit 240 may set the weight for the position of thetarget larger.

The update unit 240 may calculate the current position of the tracker'sobject using the predicted position and the weighted position.

As described above, since the update unit 240 determines a weight forthe position of the target, the detection result by a camera 20 near tothe target can be more heavily weighted in the prediction of thedetected position of the object. Therefore, the object trackingapparatus 10 can improve the prediction accuracy of the position of theobject.

The update unit 240 may update the latest predicted position of theobject included in information related to the object stored in thememory unit 220 with the calculated current position of the object.

The updating of the likelihood of a tracker performed by the update unit240 will be described.

If a tracker's object is far from a camera 20, the size of the objectmay become small. Therefore, it may become difficult for a detectionunit 100 to detect such an object.

In a case where the appearance of an object included in a frame isdifferent from the appearance of an object used in learning,recognition-type object detection performed by a recognition-type objectdetection unit 111 of a detection unit 100 will be described. The casewhere the appearance of the object included in the frame is differentfrom the appearance of the object used in learning may be, for example,a case where the depression angle of a camera 20 to the object, thedepression angle being assumed from the position of the tracker'sobject, and the depression angle of the camera 20 to the object used inthe learning are greatly different from each other. In such a case, itmay become difficult for the recognition-type object detection unit 111of the detection unit 100 to detect the object included in the frame.

In a case where it is difficult to detect the object, there may be apossibility that the object included in the frame remains undetected. Inthis case, there may be a possibility that there is no target that isassociated with the tracker related to this object.

In some embodiments, the update unit 240 may reduce the variation of thelikelihood of the tracker related to an object in a situation where itis difficult to detect of the object, among trackers not associated toany target.

In such a way, the update unit 240 may alleviate an adverse effect ontracking in a case where an object is difficult to detect, and canintensely reflect a detection result obtained by a camera, using whichthe object is easily detected, in the likelihood of the correspondingtracker. In tracking of the object on the next frame, because theassociation unit 230 performs association on the basis of thislikelihood of the tracker, the integral tracking unit 200 can greatlyimprove the accuracy of the object tracking.

The update unit 240 may update the likelihood of the tracker calculatedby the association unit 230 and the likelihood of the tracker, thevariation of which is reduced, among the likelihoods of trackers storedin the memory unit 220.

The update of the motion model of a tracker's object performed by theupdate unit 240 will be described. For example, a case where theintegral tracking unit 200 performs object tracking by estimating theposition of an object using a Kalman filter will be described. In thiscase, the update unit 240 may update the state of the Kalman filter bysubstituting the position coordinate values of a tracker's objectassociated with a target for the update expression of the state variableof the Kalman filter, which is stored in the memory unit 220, as adetected position coordinate value.

In some embodiments, besides the above updating, the update unit 240 mayupdate other parameters of the tracker and the like stored in the memoryunit 220.

For example, there may be a case where an object itself changes itsposture. For example, if an object is a person, when the person crouchesdown or bends down, the apparent height of the person may change. Asdescribed above, when not only the motion model of the object but alsothe size of the object or the like changes, the update unit 240 mayupdate information related to the changes among information stored inthe memory unit 220.

In some embodiments, if parameters of the tracker include weights whichrepresent a probability that a tracker's object exists, reliability of atracking result, and the like, the weights may vary in accordance withthe result of association processing performed by the association unit230. Therefore, the update unit 240 may update parameters such as theseweights.

The update unit 240 may generate a tracker or delete a tracker as partof tracker update processing. After the association processing by theassociation unit 230, the update unit 240 may determine whether there isa target that is not associated with any tracker or not. There may be apossibility that the target, which is not associated with any tracker,is an object that has newly appeared within an area that thecorresponding camera 20 can capture. Therefore, if there is a targetthat is not associated with any tracker, the update unit 240 maydetermine whether this target can be regarded as an object that hasnewly appeared within the area or not.

In some embodiments, if there is a target that is not associated withany tracker, the update unit 240 may evaluate a probability that thistarget exists. In this case, the update unit 240 may determine whetherthis probability is equal to or more than a predetermined value or not.If this probability is equal to or more than the predetermined value,the update unit 240 may determine that this target is an object that hasnewly appeared within the area. The update unit 240 may generate atracker related to the object (e.g., target) that is determined to be anobject that has newly appeared within the area.

In some embodiments, the update unit 240 may determine whether there isa tracker that is not associated with any target or not. There may be apossibility that the tracker that is not associated with any target is atracker related to an object that has disappeared from an area that thecorresponding camera 20 can capture (e.g., an object that has moved fromthe inside of the area to the outside of the area). Therefore, if thereis a tracker that is not associated with any target, the update unit 240may determine whether or not this tracker can be regarded as a trackerrelated to an object that has disappeared from the inside of the area.

In some embodiments, if there is a tracker that is not associated withany target, the update unit 240 may evaluate a probability that anobject related to this tracker exists. The update unit 240 may determinewhether this probability is smaller than a predetermined value or not.If this probability is smaller than the predetermined value, the updateunit 240 may determine that the object related to this tracker is anobject that has disappeared from the inside of the area. The update unit240 may delete the tracker related to the object that is determined tohave disappeared from the inside of the area.

A probability that an object exists may be calculated from thelikelihood of the corresponding tracker. In some embodiments, if thereis a tracker that is not associated with any target, the update unit 240may decrease the likelihood of this tracker. If the value of thelikelihood of the tracker gets smaller than a predetermined threshold,the update unit 240 may delete the tracker.

The update unit 240 may generate a tracking result on this frame withtrackers that exist to the end. The update unit 240 may output, forexample, information indicating the positions of trackers, the sizes oftrackers' objects, and the like among these trackers as informationindicating the tracking result of object tracking (trackinginformation).

As described above, with the object tracking apparatus 10 according toembodiments of the present disclosure, object tracking may be performedon camera images output from respective cameras 20 in a chronologicalorder corresponding to time information included the camera videos.Objects detected from respective video data of the plurality of cameras20 may be detected by integrating detection results with high accuracyfor the respective cameras 20, and by using tracking results in whichthe integrated detection result(s) and past tracking results arereflected. Therefore, the tracking accuracy of object tracking performedby the integral tracking unit 200 of the object tracking apparatus 10can be improved.

An example of flow of object tracking processing of the object trackingapparatus 10 according to the embodiments of the present disclosure willbe described with reference to FIG. 8. FIG. 8 is a flowchartillustrating an example of an object tracking processing methodaccording to embodiments of the present disclosure. In some embodiments,the processing method can be performed by object tracking apparatus 10of FIG. 2.

As illustrated in FIG. 8, in step S81, a recognition-type objectdetection unit 111 of a detection unit 100 may receive a camera videofrom a camera 20 that is associated with the detection unit 100including the corresponding object detection unit 110.

In step S82, the detection unit 100 may check whether or not the frameof the received camera video is the first frame output from the camera20. If the frame is the first frame (“YES” in step S82), the flow mayadvance to step S85.

If the frame of the received camera video is not the first frame (“NO”in step S82), in step S83, the corresponding individual coordinatetransformation unit 130 of the detection unit 100 may transform trackinginformation related to the previous frame output from the integraltracking unit 200 into tracking information represented in theindividual coordinate system.

In step S84, the searching area setting unit 112 of the object detectionunit 110 included in the detection unit 100 may set a searching area foran object on the current frame using the tracking informationtransformed in step S83.

In step S85, the recognition-type object detection unit 111 of thedetection unit 100 may detect the object from the received camera video.

In step S86, the individual coordinate transformation unit 130 of thedetection unit 100 may transform the detection result detected by therecognition-type object detection unit 111 into a detection resultrepresented in the common coordinate system.

In step S87, the prediction unit 210 of the corresponding integraltracking unit 200 may predict the position of the object on the currentframe using tracker information.

In step S88, the association unit 230 of the integral tracking unit 200may associate an object (e.g., a target) included in the detectionresult with a tracker.

In step S89, the update unit 240 of the integral tracking unit 200 mayupdate tracker information related to the position of the tracker'sobject, the motion model of the object, and the like.

In step S90, the update unit 240 of the corresponding integral trackingunit 200 may generate and/or delete a tracker. The object trackingapparatus 10 may repeat this processing until any frame is not inputinto the detection unit 100.

Advantageous Effect

As described above, in the object tracking apparatus 10 according to theembodiments of the present disclosure, an object can be tracked with ahigher accuracy. This may be because a detection unit 100 detects anobject from output information of a camera 20 on the basis of trackinginformation related to the output information before the correspondingoutput information (e.g., the frame of the corresponding video).Further, this may be because the integral tracking unit 200 tracks theobject on the basis of plurality of detection results output by therespective detection units 100, and generates tracking information ofthe object represented in the common coordinate system.

For example, if there is an object that is not viewable to a firstcamera 20 but viewable to a second camera 20, the object trackingapparatus 10 may use the tracking result of the object that is notviewable to the first camera 20 for object detection related to a videoof this first camera 20. In this case, when this object appears withinan area that is viewable to the first camera 20, the correspondingdetection unit 100 can appropriately detect this object. Therefore, theobject tracking apparatus 10 can perform the tracking of this objectwith high accuracy.

For at least these reasons, the object tracking apparatus 10 can raisethe accuracy of object detection in comparison with a case where thetracking result related to the previous frame is not used. Because theobject tracking apparatus 10 performs object tracking using thedetection results from a plurality of detection units, the accuracy oftracking results may also be improved as a whole.

As described above, the object tracking apparatus 10 according toembodiments of the present disclosure can extract the trajectory of aperson or the like moving across areas that are captured by individualsof plurality of cameras 20. Therefore, the tracking result obtained bythe object tracking apparatus 10 can be used as fundamental informationfor marketing or for changing the layout of a shop by analyzing theaction of a customer who moves round the inside of a shop. In someembodiments, this tracking result can be used for detecting a person whohangs around across the areas for security reasons.

In some embodiments, because a searching area setting unit 112 sets asearching area for object detection in a camera video using a trackingresult, a recognition-type object detection unit 111 can reducesuperfluous erroneous detection. In other aspects, the recognition-typeobject detection unit 111 can speed up object detection processing.

In some embodiments, because the integral tracking unit 200 performsobject tracking using the likelihoods of targets and/or the likelihoodsof trackers, the object tracking apparatus 10 can obtain a more reliableobject tracking result. In other aspects, because the object trackingapparatus 10 performs object detection using the object tracking resultobtained in such a way, the accuracy of object tracking can be improved.Therefore, the object tracking apparatus 10 can improve the accuracy ofobject tracking as a whole.

Second Example

A second example will be described with reference to the accompanyingdrawings. Components having the same functions as the functions ofcomponents included in the drawings described in the first example willbe given the same reference symbols.

An object tracking system 2 according to embodiments of the presentdisclosure may have a configuration including an object trackingapparatus 50 instead of the object tracking apparatus 10 of the objecttracking system 1 according to the first example described using FIG. 2.Other parts of the configuration of the object tracking system 2 may bethe same as those of the object tracking system 1 illustrated in FIG. 2.

(Object Tracking Apparatus 50)

The functions of the object tracking apparatus 50 will be described withreference to FIG. 9. FIG. 9 is a block diagram illustrating an exampleof an object tracking apparatus 50 according to embodiments of thepresent disclosure. As illustrated in FIG. 9, the object trackingapparatus 50 may include a plurality of detection units (100-1 to100-N), an integral tracking unit 200, and a display control unit 300.As is the case with the above-described first example, in the presentexample, the plurality detection units (100-1 to 100-N) may be referredto collectively as detection units 100.

The display control unit 300 may control images (e.g., extracted fromthe videos) to be displayed on a display device 30. In some embodiments,the display control unit 300 may generate display data, which istransformed into data displayable on the display device 30, fromtracking information output from the integral tracking unit 200, andtransmit the display data to the display device 30. The trackinginformation output from the integral tracking unit 200 may berepresented in a common coordinate system. In some embodiments, thedisplay control unit 300 may generate display data that is transformedinto data displayable on the display device 30 in the common coordinatesystem.

In this case, the integral tracking unit 200 may output information forthe flow lines of objects to be displayed on the display device 30 (forexample, information indicating the past positions of trackers' objects)to the display control unit 300 as tracking information. This trackinginformation may be either the same as or different from information tobe provided to the detection units 100.

The display device 30 may display the received display data on itsscreen. As described above, the object tracking apparatus 50 can providea tracking result to a user.

A detection unit 100 of the object tracking apparatus 50 according tothe present example may generate display data, which is obtained bytransforming a searching area set by the searching area setting unit 112of the corresponding object detection unit 110 into data displayable onthe display device 30, and transmit the display data to the displaydevice 30. Searching area information output by the searching areasetting unit 112 may be represented in the individual coordinate systemof the camera 20. In some embodiments, the display control device 300may generate display data displayable in the corresponding individualcoordinate system on the display device 30 using camera parameters of acamera 20 associated with the detection unit 100 that outputs thesearching area information.

The display device 30 may display the received display data on itsscreen. As described above, the object tracking apparatus 50 can providethe searching area to the user using the searching area information ofthe corresponding object output from each detection unit 100.

In some embodiments, there may be a plurality of display devices 30. Forexample, a combination of two display devices can be configured in suchaway that one display device 30 receives display data represented in thecommon coordinate system, and the other display device 30 receivesdisplay data represented in individual coordinate systems, andrespective display devices 30 display the display data they receive ontheir screen. In other aspects, one display region of a display device30 may be divided into a plurality of sub-regions, and the display datamay be divided among the plurality of sub-regions for displaying. Asdescribed above, the data display method of the display device 30according to the present example may not be limited to a specificmethod.

In some embodiments, the display control unit 300 may be configured tobe included in each detection unit 100. FIG. 10 is a block diagramindicating an example of a detection unit 100 of the object trackingapparatus 50 according to an illustrative embodiment. As illustrated inFIG. 10, the detection unit 100 may include an object detection unit110, a common coordinate transformation unit 120, an individualcoordinate transformation unit 130, and a display control unit 150. Insome embodiments, the object detection unit 110 may include arecognition-type object detection unit 111, and a searching area settingunit 112 as is the case with the object detection unit 110 illustratedin FIG. 5.

The searching area setting unit 112 illustrated in FIG. 10 may outputsearching area information indicating a set searching area to thedisplay control unit 150. The display control unit 150 may generatedisplay data that is transformed into data displayable on the displaydevice 30 in the common coordinate system as is the case with thedisplay control unit 300. The searching area information output by thesearching area setting unit 112 may be represented in the individualcoordinate system. In some embodiments, the display control unit 150 maygenerate display data displayable in the individual coordinate system onthe display device 30 using camera parameters of a camera 20 associatedwith the detection unit 100 that includes the display control unit 150.

The display control unit 150 may transmit the generated display data tothe display device 30. The display device 30 may display the receiveddisplay data on its screen.

Application Example

An application example of the object tracking apparatus 50 according toembodiments of the present disclosure will be described with referenceto FIGS. 11 to 14. FIGS. 11 to 14 are diagrams illustrating applicationexamples of the object tracking apparatus 50 according to embodiments ofthe present disclosure.

FIG. 11 is a diagram illustrating an example of the interior of a roomin which a rack R1, a rack R2, and plurality of cameras (A to F) areinstalled and in which is viewed from a direction opposite to thedirection of gravitational force. As illustrated in FIG. 11, the lateraldirection of FIG. 11 is set to the X-axis in the common coordinatesystem, and the longitudinal direction of FIG. 11 is set to the Y-axis.The rack R1 and the rack R2 may be installed on the X-axis in such a waythat the longitudinal directions of the rack R1 and the rack R2 are inparallel with the Y-axis.

The camera A may be installed in the position near to the doorway of theroom. In this example, it is assumed that all the parts of the interiorof the room can be captured by any of the cameras A to F. In someembodiments, as illustrated in FIG. 11, the space of the interior of theroom in which the plurality of cameras (A to F) are installed mayinclude a capturing space. In some embodiments, the cameras A to F maycapture a space common to all the cameras.

FIG. 12 is a diagram illustrating two figures that represent,respectively, an example of a video captured by the camera A and anexample of an image captured by the camera B. The upper figure in FIG.12 can be a figure illustrating a certain frame of a video captured bythe camera A. The lower figure in FIG. 12 can be a figure illustrating aframe of a video captured by the camera B. Coordinate values in theseframes may be represented by coordinate values in an individualcoordinate system for each camera.

In some embodiments, the object tracking apparatus 50 according to theembodiments of the present disclosure may be configured in such a waythat videos captured by the cameras 20 are displayed on the displaydevice 30.

As illustrated in FIG. 12, the video captured by the camera A mayinclude a person C1. Because the camera A is installed near to thedoorway, this video may include the doorway. The video captured by thecamera B may include the person C1 and a person C2.

The person C2 may be hidden by the rack R1 viewed from the camera A.Therefore, at the time when the videos in FIG. 12 are captured, theperson C2 may be an object not viewable to the camera A. If these framesof the videos are respectively a frame of the first video captured bythe camera A and a frame of the first image captured by the camera B,there are no preceding frames from any cameras. Thus, there may be notracking information related to the previous frame before each frame. Insome embodiments, the object tracking apparatus 50 may detect objectsfrom these frames, and generate tracking information.

The searching area setting unit 112 may set a searching area for anobject on the next frame of the video captured by the camera A usingtracking information represented in the individual coordinate system.The searching area setting unit 112 may set a searching area for anobject on the next frame of the video captured by the camera B usingtracking information represented in the individual coordinate system.

FIG. 13 is a diagram illustrating some examples of searching areasdisplayed on the display device 30. The upper figure in FIG. 13 may beexamples illustrating searching areas for objects on a frame output fromthe camera A, and the lower figure in FIG. 13 may be examplesillustrating searching areas for objects on a frame output from thecamera B.

As illustrated in the upper figure in FIG. 13, the searching areasetting unit 112 may obtain a searching area A1 with reference to theposition of the person C1 in the upper figure in FIG. 12. The searchingarea setting unit 112 may obtain an area in the vicinity of the doorwayleading to the interior of the room as a searching area N1. Thesearching area setting unit 112 may obtain two outer sides of the frameas searching areas N2 and N3. The searching area setting unit 112 mayoutput information including searching areas A1, N1 to N3 to therecognition-type object detection unit 111, and the display control unit150 or the display control unit 300 as searching area information. Thedisplay control unit 150 or the display control unit 300 may transform asearching area indicated by this searching area information into displaydata displayable on the screen of the display device 30, and transmitthe display data to the display device 30.

The display device 30, which receives the display data from the displaycontrol device 150 or the display control device 300, may display thesearching area on its screen as illustrated in the upper figure in FIG.13.

The lower figure in FIG. 13 will be described. As illustrated in thelower figure in FIG. 13, the searching area setting unit 112 may obtaina searching area B1 and a searching area B2 respectively with referenceto the position of the person C1 and the position of the person C2 inthe lower figure in FIG. 12. The searching area setting unit 112 mayobtain four outer sides of the frame as searching areas N4 to N7. Thesearching area setting unit 112 may output information includingsearching areas B1, B2, N4 to N7 to the recognition-type objectdetection unit 111, and the display control unit 150 or the displaycontrol unit 300 as searching area information. The display control unit150 or the display control unit 300 may transform a searching areaindicated by this searching area information into display datadisplayable on the screen of the display device 30, and transmit thedisplay data to the display device 30.

The display device 30, which receives the display data from the displaycontrol device 150 or the display control device 300, may display thesearching area on its screen as illustrated in the lower figure in FIG.13.

In some embodiments, the display device 30 can display the sub-areas ofthe searching area in different respective modes. For example, thedisplay device 30 may display the sub-area of the searching area thathave been already detected and the sub-area of the searching arearelated to outer sides of a frame in different respective colors.

The integral tracking unit 200 may generate trackers related to theperson C1 and the person C2 who are detected on the subsequent frames.The integral tracking unit 200 may output information for displaying therespective trajectories of the person C1 and the person C2 to thedisplay control unit 300 as tracking information.

The display control unit 300 that receives the tracking information fromthe integral tracking unit 200 may transform the tracking informationinto display data that is displayable on the display device 30, andtransmit the transformed display data to the display device 30.

The display device 30 may display the display data received from thedisplay control unit 300 on its screen. FIG. 14 is a figure illustratingan example of the trajectories indicating the respective trackingresults of the person C1 and the person C2 that the display device 30displays on its screen (display screen). As illustrated in FIG. 14, itis assumed that the tracking result of an object is displayed on the X-Yplane in the common coordinate system in this application example. InFIG. 14, the trajectory of the person C1 is depicted by a solid line,and the trajectory of the person C2 is depicted by a one-dot chain line.In this way, the display device 30 can display the tracking results ofobjects on its screen.

Third Example

A third example will be described with reference to the accompanyingdrawings. Components having the same functions as the functions ofcomponents included in the drawings described in the first example andthe second example will be given the same reference symbols.

An object tracking apparatus 10 according to embodiments of the presentdisclosure includes detection units 400 instead of the detection units100 of the object tracking apparatus 10 illustrated in FIG. 1. Theconfiguration of this detection unit 400 will be described withreference to FIG. 15. FIG. 15 is a block diagram illustrating an exampleof a detection unit 400 of the object tracking apparatus 10 according toan illustrative embodiment.

The detection unit 400 may include an object detection unit 140 insteadof the object detection unit 110 of the detection unit 100 illustratedin FIG. 4 and FIG. 5. In some embodiments, the detection unit 400 mayinclude a memory unit 160. In other aspects, the detection unit 400according to the embodiments of the present disclosure may include theobject detection unit 140, a common coordinate transformation unit 120,an individual coordinate transformation unit 130, and the memory unit160.

In this example, the object tracking apparatus 10 is configured toinclude the object detection units 140 instead of the object detectionunits 110 of the detection units 100 of the object tracking apparatus 10according to the first example. The present disclosure is not limited tothe above configuration, and the configuration of the object trackingapparatus 10 according to the present example can include the objectdetection units 140 instead of the object detection units 110 of thedetection units 100 of the object tracking apparatus 50 according to thesecond example. In some embodiments, the detection unit 100 according tothe present example can be configured to output data to be displayed tothe display control unit 150 or to the display control unit 300.

The memory unit 160 may store camera parameters for each camera 20 thatare used in transformation between the coordinate systems. In someembodiments, the memory unit 160 may store information indicating therange of coordinate values in the common coordinate system that is usedfor the individual coordinate transformation unit 130 to check whetheror not coordinate values in the common coordinate system included intracking information is within an area that can be captured by thecorresponding camera 20. The memory unit 160 may store a video that iscaptured by the camera 20. This video may be temporarily stored.

As illustrated in FIG. 15, the following description will be madeassuming that the memory unit 16 is embedded in the detection unit 400.The present disclosure may not be limited to this configuration. Thememory unit 160 may be installed in the object tracking apparatus 10independently of the detection unit 400. In some embodiments, the memoryunit 160 may be realized by a separate memory device or the likeindependently of the object tracking apparatus 10.

The detailed functional configuration of the object detection unit 140of the detection unit 400 will be described with reference to FIG. 16.FIG. 16 is a functional block diagram illustrating an example of thefunctional configuration of the object detection unit 140 of thedetection unit 400 according to an illustrative embodiment. Asillustrated in FIG. 16, the object detection unit 140 may include arecognition-type object detection unit 141, a nonrecognition-type objectdetection unit 142, a detection parameter update unit 143, and adetection result integration unit 144.

In this example, object detection that uses a dictionary (e.g., adiscriminator) may be referred to as “recognition-type objectdetection”. In this example, object detection that does not use adiscriminator may be referred to as “nonrecognition-type objectdetection”.

The recognition-type object detection unit 141 may detect objects from acamera video input into the recognition-type object detection unit 141.The recognition-type object detection unit 141 may perform objectdetection on the entirety of a frame. As depicted by a dashed line, therecognition-type detection unit 141 may perform object detection on thebasis of searching area information output from the detection parameterupdate unit 143 as described below. In this case, the recognition-typeobject detection unit 141 may perform object detection in the same wayas the recognition-type object detection unit 111 described in the firstexample does.

In a case where the searching area information is not output from thedetection parameter update unit 143, the recognition-type objectdetection unit 141 may not perform object detection on the entirety of aframe, but perform object detection on the basis of another criterion.For example, the recognition-type object detection unit 141 may performobject detection in an area within which the silhouette of an objectexists and the surrounding area of the area using the silhouetteinformation of the object.

The recognition-type object detection unit 141 may output the detectionresult of the object detection to the detection result integration unit144 as a first detection result.

The recognition-type object detection unit 141 may extract theappearance features of the object at this time in preparation for thebelow-described nonrecognition-type object detection unit 142 to performobject detection. The appearance features of an object may includeinformation related to the color, pattern, and shape of the object. Thepresent disclosure may not be limited to the above information. Therecognition-type object detection unit 141 may extract these features asthe appearance features of the object. In this case, it may not bealways necessary that an area used for object detection performed by therecognition-type object detection unit 141 is the same as an area usedfor object detection performed by the nonrecognition-type objectdetection unit 142. For example, if an object is a person, it is assumedthat the recognition-type object detection unit 141 detects the head ofthe person, and the nonrecognition-type object detection unit 142detects the head to the area of the clothes of the person. In this case,the recognition-type object detection unit 141 may extract appearancefeatures of the object from an area including the area of the clothes ofthe person. The recognition-type object detection unit 141 may outputthe extracted features as template information as well as informationindicating an area used for the extraction. In some embodiments, therecognition-type object detection unit 141 may store the featuresthemselves, and output information for identifying the features.

The detection parameter update unit 143 may receive tracking informationrepresented in the individual coordinate system from the individualcoordinate transformation unit 130. The detection parameter update unit143 may obtain parameters for object detection (hereinafter referred toas detection parameters) using this information. These detectionparameters may be parameters necessary for object detection processing.The detection parameters may include, for example, the predictedposition of an object on the current frame, a searching area to whichobject detection is applied, the size of a template used for templatematching, the features of the template of a target associated with atracker in the past, etc. The detection parameters may exclude some ofthe above information, and the detection parameters may includeparameters for object detection performed by the nonrecognition-typeobject detection unit 142. The detection parameters may includeinformation of a target associated with a tracker in the tracking resultof the object on the previous frame.

For example, the detection parameter update unit 143 may obtain theposition at which an object exists on the current frame as a predictedposition on the basis of the tracking information of the object that isa target (e.g., an object detected on the previous frame) and associatedwith a tracker. This prediction processing may be performed in a similarway to the prediction processing of a predicted position performed bythe searching area setting unit 112 according to the first example. Thedetection parameter update unit 143 may obtain an area including thispredicted position as a prediction area.

For example, the detection parameter update unit 143 may obtain an areato which object detection by template matching is applied with the aboveprediction area as the center of the area, and include this area intothe searching area of the object included in the detection parameters.

The detection parameter update unit 143 may obtain the detectionparameters for respective objects included in tracking information. Thedetection parameter update unit 143 may update the obtained detectionparameters as detection parameters used for object detection processing.The detection parameter update unit 143 may output these detectionparameters to the nonrecognition-type object detection unit 142.

The detection parameter update unit 143 may obtain the searching area ofan object using tracking information transformed into coordinate valuesin the individual coordinate system as is the case with theabove-described searching area setting unit 112 of the detection unit100 according to the first example. The detection parameter update unit143 may output searching area information indicating the obtainedsearching area of the object to the recognition-type object detectionunit 141.

The nonrecognition-type object detection unit 142 may receive thedetection parameters from the detection parameter update unit 143. Thenonrecognition-type object detection unit 142 may detect an object froma camera video input into the nonrecognition-type object detection unit142 on the basis of the received detection parameters. Thisnonrecognition-type object detection unit 142 may perform objectdetection on the basis of the similarity of the appearance of the objectdetected on the previous frame unlike the recognition-type objectdetection unit 141.

In some embodiments, when an object is detected on the previous frame,the nonrecognition-type object detection unit 142 may store the imagefeatures of the region of the object (or a partial image of thedetection region itself) as a template. The nonrecognition-type objectdetection unit 142 may perform object detection by checking whether aregion similar to this stored template exists on the current frame ornot using template matching. The image features used in this case maybe, for example, features indicated by information related to a colorpattern and a color distribution, information related to an edgedistribution and a luminance gradient distribution, or a combination ofsome of the above information.

The detection parameters used when the nonrecognition-type objectdetection unit 142 performs object detection may be controlled bydetection parameters output from the detection parameter update unit143. In some embodiments, the nonrecognition-type object detection unit142 may perform object detection by performing template matching on thepredicted position of an object, which is predicted by the detectionparameter update unit 143, and its vicinity. In other aspects, thenonrecognition-type object detection unit 142 may set the searching areaof template matching with its center set to a predicted object existencearea, and perform template matching on its vicinity. In this case, thenonrecognition-type object detection unit 142 may take intoconsideration that the apparent size of an object changes in accordancewith the displacement of the position of the object. This change may becalculated using camera parameters. In some embodiments, aftercalculating the change of the size of the object, and reflecting thechange in the template, the nonrecognition-type object detection unit142 may perform template matching.

Information of the template used by the nonrecognition-type objectdetection unit 142 for template matching may be information related tothe features extracted by the recognition-type object detection unit 141in the object detection processing on the previous frame.

As describe above, because the nonrecognition-type object detection unit142 performs object detection on the basis of the tracking results of anobjects that are tracked by the integral tracking unit 200, thenonrecognition-type object detection unit 142 can improve the accuracyof object detection in comparison with a case where the above trackingresults are not used.

The nonrecognition-type object detection unit 142 may output thedetection result of the object detection to the detection resultintegration unit 144 as a second detection result.

The detection result integration unit 144 may receive the firstdetection result from the recognition-type object detection unit 141.The detection result integration unit 144 may receive the seconddetection result from the nonrecognition-type object detection unit 142.The detection result integration unit 144 may integrate the firstdetection result and the second detection result. The detection resultintegration unit 144 may output the integrated result to the commoncoordinate transformation unit 120 as the detection result of the objectdetection performed by the object detection unit 140.

There may be some objects that are included both in the first detectionresult and in the second detection result, and others may be includedeither in the first detection result or in the second detection result.In some embodiments, the detection result integration unit 144 mayintegrate the first detection result and the second detection result byassociating objects included in the first detection result with objectsin the second detection result. In this association, the degree ofoverlap among object regions may be used.

In some embodiments, the detection result integration unit 144 maycalculate an overlap ratio between the object regions of respective twoobjects (for example, an overlap ratio between the object circumscribingrectangles related to the two objects), and if the overlap ratio islarger than a predetermined value, the object included in the firstdetection result and the object included in the second detection resultmay be associated with each other.

The detection result integration unit 144 may associate any two objectswith each other based on a formula that calculates a weight based on anoverlap ratio between the object regions of the two objects. Forexample, after transforming the overlap ratio into a cost using amonotonically nonincreasing function, the detection result integrationunit 144 may associate the two objects with each other by calculating anoptimal association using a Hungarian method or the like.

As a result of the association, if the values used for the association(for example, the overlap ratio or the cost) are larger than apredetermined value, the detection result integration unit 144 mayintegrate the corresponding first detection result and the correspondingsecond detection result at this moment. In some embodiments, withoutintegrating the corresponding first detection result and thecorresponding second detection result at this moment, the detectionresult integration unit 144 may generate information indicating that therespective two objects are associated with each other. As a result,after making a detection result by combining the first detection resultand the second detection result and adding the information, whichindicates that the association can be made, to the detection result, thedetection result integration unit 144 may output the detection result asthe detection result of the object detection unit 140, and performtracking using information related to the association when integraltracking is performed.

The nonrecognition-type object detection unit 142 may output a seconddetection result on the basis of the tracking result of an object on theprevious frame. In some embodiments, there may be a case where thesecond detection result is generated later than the corresponding firstdetection result is generated. In such a case, the detection integrationunit 144 may temporarily store the first detection result in a memoryregion such as a buffer in the detection integration unit 144 or in thememory unit 160. At the time when the detection result integration unit144 receives a second detection result related to a frame correspondingto a frame related to which the first detection result is generated, thedetection result integration unit 144 may integrate both results.

As described above, the detection unit 400 of the object trackingapparatus 10 according to embodiments of the present disclosure mayoutput the result of integration of the result of object detectionperformed by the recognition-type object detection unit 141 and theresult of object detection performed by the nonrecognition-type objectdetection unit 142 as a detection result. In this case, thenonrecognition-type object detection unit 142 may detect an object byperforming template matching on the basis of the tracking result ofobjects tracked by the integral tracking unit 200. As described above,the detection unit 400 can improve the accuracy of object detection incomparison with a case where object detection is performed only byrecognizing an object (recognizing-type object detection).

Therefore, the object tracking apparatus 10 can perform object trackingmore accurately.

Fourth Example

A fourth example will be described with the accompanying drawings.Components having the same functions as the functions of componentsincluded in the drawings described in the above-described examples willbe given the same reference symbols.

An object tracking apparatus 10 according to embodiments of the presentdisclosure may have a configuration including an integral tracking unit500 instead of the integral tracking unit 200 of the object trackingapparatus 10 illustrated in FIG. 1. The configuration of this integraltracking unit 500 will be described with reference to FIG. 17. FIG. 17is a block diagram illustrating an example of an integral tracking unit500 of the object tracking apparatus 10 according to embodiments of thepresent disclosure. As illustrated in FIG. 17, the integral trackingunit 500 may include a buffer unit 510, a prediction unit 210, a memoryunit 220, an association unit 530, and an update unit 240.

The present example will be described assuming that the object trackingapparatus 10 according to embodiments of the present disclosure isconfigured to include the integral tracking unit 500 instead of theintegral tracking unit 200 of the object tracking apparatus 10 accordingto the first example. The present disclosure may not be limited to theabove configuration, and the configuration of the object trackingapparatus 10 according to the embodiments of the present disclosure mayinclude the integral tracking unit 500 instead of the integral trackingunit 200 of the object tracking apparatus 50 according to the secondexample. In some embodiments, the integral tracking unit 500 may beconfigured to output data to be displayed to a display control unit 300.

In some embodiments, a detection unit that outputs a detection result tothe integral tracking unit 500 in this example may be the detection unit400 described in the third example.

The buffer unit 510 may be a storage section that temporarily stores adetection result that is output from a detection unit 100 andrepresented in a common coordinate system. Among data (e.g., detectionresults) buffered in the buffer unit 510, data which is detected fromcamera videos including time information indicating times within apredetermined time period may be obtained by the association unit 530.This predetermined time period may be a cyclic time period. Theassociation unit 530 may perform object tracking using one or moredetection results obtained in a certain cycle. In this way, because theintegral tracking unit 500 performs object tracking using a plurality ofcamera videos among videos captured by respective cameras 20, theintegral tracking unit 500 may also be referred to as a batch trackingunit.

The object tracking (hereinafter referred to as batch integral tracking)performed by this integral tracking unit 500 will be described withreference to FIG. 18. FIG. 18 is a diagram describing object batchtracking processing according to embodiments of the present disclosure.In some embodiments, the batch integral tracking of FIG. 18 can beperformed by integral tracking unit 500. As is the case with FIG. 7,FIG. 18 may be an example illustrating timing at which each of a cameraA, a camera B, and a camera C (of cameras 20) obtains an image in thecase where the number of cameras is three. In FIG. 18, each ofhorizontal axes is a time axis and the righter a time point is locatedalong the time axis, the later time the time point indicates. Asillustrated in FIG. 18, it is assumed that the camera A obtains imagesat the time t1, t5, and t8. Similarly, it is assumed that the camera Bobtains images at the time t2, t4, t6, and t9, and that the camera Cobtains images at the time t3, and t7.

Object detection may be performed on the images obtained at theserespective timings in chronological order. The following explanationwill be made under the assumption that the times illustrated in FIG. 18are almost equal to times at which the corresponding detection resultsof objects are output. In other words, it is assumed that the time t1 isa time at which a detection result related to a frame of a videocaptured by the camera A is output from the detection unit 100 and atwhich the detection result is buffered in the buffer unit 510.

The lowermost time axis in FIG. 18 is an example illustrating a cyclictime period.

The association unit 530 may obtain a detection result, which isdetected from a camera video including time information indicating atime within a predetermined time period, among one or plurality ofdetection results buffered in the buffer unit 510. As described above,this predetermined time period may be a cyclic time period. In thisexample, it is assumed that the time when one or plurality of detectionresults are buffered is equal to the time when the respective cameravideos are captured. In some embodiments, the association unit 530 mayobtain one or plurality of buffered detection results at a predeterminedcycle.

In some embodiments, the association unit 530 may obtain detectionresults buffered during the first time period T1. In other words, theassociation unit 530 may obtain detection results buffered at the timest1, t2, and t3. A detection result buffered at the time t1 may be adetection result related to a frame of a video captured by the camera A.A detection result buffered at the time t2 may be a detection resultrelated to a frame of a video captured by the camera B, and a detectionresult buffered at the time t3 may be a detection result related to aframe of a video captured by the camera C. In some embodiments, theassociation unit 530 may obtain a plurality of detection results, whichare buffered in the buffer unit 510 during a predetermined time period(in this case, during the time period T1) and which are detectionresults related to frames of respective videos captured by individualsof the plurality of cameras 20, from the buffer unit 510. Theassociation unit 530 may perform object tracking using the obtaineddetection results.

During the time periods T2, T3, and T4, the association unit 530 mayperform object tracking using detection results obtained during thesecyclic time periods in the same way as above.

The configuration of the present example is described under theassumption that the association unit 530 obtains data (e.g., theplurality of detection results), which are buffered in the buffer unit510, at a predetermined time period. In some embodiments, theassociation unit 530 may be configured to receive these data from thebuffer unit 510 at a predetermined time period. In other words, thebuffer unit 510 may transmit these data to the association unit 530 at apredetermined time period.

With reference to FIG. 17, the association unit 530 of the integraltracking unit 500 will be described.

The association unit 530 may obtain distances among targets included inthe obtained detection results using the positions of the targets, andassociate two targets, the distance between which is short, with eachother. At this time, the association unit 530 may perform associationusing the distances among the targets by means of a Hungarian method orthe like. In some embodiments, the association unit 530 may use thesimilarity in the appearance features of the targets in addition to thedistances among the targets. For example, there may be a highpossibility that two targets whose positions are near to each other andwhose colors are similar to each other correspond to the same object.Therefore, the association unit 530 may perform association using suchfeatures. The types of features for determining the similarity in theappearance features may not be limited to the colors of targets, and thetypes of features may be the patterns of targets and the like.

The association unit 530 may integrate the detection resultscorresponding to the targets that are associated with each other. Insome embodiments, after associating the targets with each other, theassociation unit 530 may obtain the position of the corresponding objectusing respective detection results corresponding to the targetsassociated with each other. At this time, the association unit 530 mayevaluate the likelihood and/or the accuracy of the predicted position ofeach target, and set the position, which makes this accuracy maximum, tothe position of the corresponding object.

The association unit 530 may weigh the position of each target on thebasis of the accuracy of predicted position determined by an angle(e.g., a depression angle or an elevation angle) of the correspondingcamera 20 to the target, a distance from the camera 20 to each target,and the like. The association unit 530 may calculate a statistic valuesuch as an average value from the weighted position, and set theposition indicated by the calculated statistic value to the position ofthe object.

The association unit 530 may set the obtained position of the object tothe position of the target related to a cycle in which the correspondingdetection result is obtained. The association unit 530 may performassociation using the position of this target as is the case with theassociation unit 230 according to the first example. The associationprocessing and the subsequent processing are the same as those performedby the integral tracking unit 200 described in the first example.

Before performing association among targets, the association unit 530may associate targets with trackers, and the association unit 530 mayintegrate the detection results corresponding to respective associatedtargets. In some embodiments, if there are plurality of targetsassociated with the same tracker, the association unit 530 may associatethese targets with each other. In this case, the association unit 530may perform association while taking into consideration the likelihoodsand/or accuracy of the predicted positions of respective targets. Insuch a way, the association unit 530 may evaluate detection results onthe basis of the information, and may integrate the detection resultscorresponding to respective associated targets associated with the sametracker.

As described above, the object tracking apparatus 10 according to thepresent example may perform object tracking using all detection resultsrelated to camera videos captured by respective cameras 20 duringpredetermined time periods. As a result, it may become possible that theobject tracking apparatus 10 easily performs object tracking processingin which the detection results of objects are given priority.

If the frame rates of all the cameras 20 are steady and the same, it maybecome possible to include the frames of all the cameras 20 in apredetermined time period by appropriately setting the predeterminedtime period in consideration of the frame intervals. Therefore, theobject tracking apparatus 10 according to the present example canperform object tracking on the frames related to all the cameras 20. Asa result, because the object tracking apparatus 10 can evaluate at thesame time the detection results related to objects that are all togetherviewable to the plurality of cameras 20, it may become possible that thereliability of the detection results is directly reflected by tracking.

Fifth Example

A fifth example according to the present disclosure will be described.In this explanation of the present example, the minimum configurationthat solves the problem of this invention will be described.

Because an object tracking apparatus 10 according to the present examplehas a configuration similar to the configuration of the object trackingapparatus 10 that has been described in the first example andillustrated in FIG. 1, the object tracking apparatus 10 according to thepresent example will be described with reference to FIG. 1.

As illustrated in FIG. 1, the object tracking apparatus 10 according tothe present example may include a plurality of detection unit (100-1 to100-N) and an integral tracking unit 200. In the present example, theplurality of detection units (100-1 to 100-N) may be referred to asdetection units 100.

Each of the plurality of detection units 100 may detect objects fromoutput information output from the corresponding sensor. The sensors aredescribed as cameras and output information of the sensors is describedas camera videos. In some embodiments, the sensors may not be limited tocameras. In some instances, each detection unit 100 may detect objectson the basis of tracking information output from the integral trackingunit 200. The detection unit 100 may output the detection result to theintegral tracking unit 200.

The integral tracking unit 200 may track one or more objects indicatedby the plurality of detection results on the basis of the detectionresults output by individuals of the plurality of detection units (100-1to 100-N). The integral tracking unit 200 may generate trackinginformation of the objects represented in the common coordinate system.The integral tracking unit 200 may output the tracking information toindividuals of the plurality of detection units (100-1 to 100-N).

As described above, the detection units 100 of the object trackingapparatus 10 according to the present example may detect objects fromthe output information output from the sensors on the basis of thetracking results of objects that are tracked by the integral trackingunit 200.

As described above, because the object tracking apparatus 10 detectsobjects from videos using the tracking result related to the previousframe, the object tracking apparatus 10 can raise the accuracy of objectdetection higher in comparison with a case where the tracking resultrelated to the previous frame is not used. Because object tracking isperformed using all the object detection results related to videoscaptured by individuals of the cameras 20, the object tracking apparatus10 can improve the accuracy of tracking in comparison with a case whereobject tracking is independently performed for each camera. Because theobject tracking apparatus 10 performs object tracking using thedetection results from a plurality of detection units, objects can betracked more accurately.

In the above examples, descriptions have been made under the assumptionthat the object tracking apparatus 10 includes detection units (100 or400) and the integral tracking unit (200 or 500). In some embodiments,these detection units and integral tracking unit may be respectivelyrealized in separate devices. In some embodiments, the detection units(100 or 400) may be realized as object detection devices by separatedevices, and the integral tracking unit (200 or 500) may be realized asan integral tracking device by a separate device. In some embodiments,the display control unit 300 may be realized as a separate displaycontrol device independently of the object tracking apparatus 50. Inother aspects, this display control device may be embedded in thedisplay device 30.

Sixth Example

A sixth example will be described below. Because the configuration of anobject tracking apparatus 10 according to the present example is similarto that of the object tracking apparatus 10 that is described andillustrated in FIG. 1 in the first example, the object trackingapparatus 10 according to the present example will be described withreference to FIG. 1. The object tracking apparatus 10 according to thepresent example may include functions that will be described as followsin addition to the functions of the object tracking apparatus 10according to the first example. In some embodiments, the presentdisclosure may not be limited to this. The function of the objecttracking apparatus 10 according to the present example may have theobject tracking apparatuses according to the above-described second tofifth example.

In the present example, an integral tracking unit 200 may obtaininformation related to the appearances of respective objects, and thisobtained information may be added to the tracking information related tothe respective objects. The detection units 100 may control the objectdetection using the information that is included in the trackinginformation output from the integral tracking unit 200 and that isrelated to the appearances of the respective objects.

This information related to the appearances of the respective objects(hereinafter, referred to as appearance information) may be informationrelated to the appearance of the respective objects when the respectiveobjects are viewed from the positions of the respective cameras 20, andthis information may be determined by the positions of the objects ofrespective trackers.

For example, there is a case where, when a certain object and anotherobject are viewed from a certain camera 20, the certain object islocated in front of the other object (e.g., being closer to the certaincamera 20). In such a case, there may be a high possibility that therear object (the other object) is overlapped by the front object (thecertain object), and that the rear object (the other object) becomes notviewable from the certain camera 20. In some instances, the integraltracking unit 200 may add information indicating such an overlappingstate between these objects as appearance information to a trackerrelated to the other object, and output the tracking result.

An example of an operation of the respective units of the objecttracking apparatus 10 according to the present example will bedescribed.

The integral tracking unit 200 may store information related to thedispositions of the respective cameras 20, for example, in a memory unit220 illustrated in FIG. 6 or the like. The information related to thedispositions of the respective cameras 20 may include, for example,information indicating positions in which the respective cameras 20 aredisposed, directions which are captured by the respective cameras 20,and the like. The integral tracking unit 200 may include informationrelated to illumination conditions such as the position and direction ofan illumination in a capturing space, the characteristics of theillumination, and well-lighted areas or low-lighted areas in thecapturing space as information related to the dispositions of therespective cameras 20. The integral tracking unit 200 may storeinformation related to the direction of the capturing space as theinformation related to the dispositions of the respective cameras 20.

As is the case with the integral tracking units 200 according to theabove-described exemplary embodiments, the integral tracking unit 200may predict the motions of the objects on the current frame indicated bythe respective trackers, and associate targets with the respectivetrackers, and the integral tracking unit 200 may obtain the positions ofthe trackers.

The integral tracking unit 200 may predict the positions of objectswhich are indicated by the respective trackers on captured imagescaptured by the respective cameras 20, using the obtained positions ofthe trackers and information related to the motion of the trackers.

The integral tracking unit 200 may predict the appearance of each objectlocated in its predicted position from each of the respective cameras 20(appearance) with reference to information related to the dispositionsof the cameras 20. In some embodiments, the integral tracking unit 200may estimate whether or not there will be an overlapping among theobjects indicated by each of the above-described respective trackers foreach of the plurality of cameras 20 in the timing at which the nextcapturing is performed.

In a case where the integral tracking unit 200 determines that there isan overlapping among objects on an captured image captured by a certaincamera 20 on the basis of the predicted appearance, the integraltracking unit 200 may generate information indicating there is apossibility that some object is overlapped and becomes not viewable(appearance information) owing to the overlapping.

For example, when there is a certain camera 20 and a certain predictedobject, the integral tracking unit 200 may determine whether or notthere is another estimated object on a line segment between the certaincamera 20 and the certain predicted object. If there is anotherpredicted object on the line segment between the certain camera 20 andthe certain predicted object, there may be a high possibility that thiscertain object is overlapped by the other object. In some embodiments,the integral tracking unit 200 may obtain information related to thisoverlapped object and the degree of overlap as appearance informationrelated to the certain object.

The integral tracking unit 200 may add this determination result to thetracking result of this certain object as the appearance information.

The integral tracking unit 200 may add the generated appearanceinformation to the tracking information of the object that is likely todisappear from the captured image captured by the certain camera 20. Inthis case, information indicating a camera 20, which captures an imageincluding an object likely to be not viewable, may be added to theappearance information.

The integral tracking unit 200 may send the tracking informationincluding the appearance information to the respective detection units100. In some embodiments, the integral tracking unit 200 may send thetracking information including the appearance information to a detectionunit 100 corresponding to a camera 20 (e.g., a certain camera 20) thatcaptures an image including an object likely to unviewable owing tooverlapping among objects. The integral tracking unit 200 may send thetracking information not including the appearance information to thedetection unit 100 corresponding to other cameras 20.

If it is known that the way an illumination is cast on an object variesin accordance with the position of the object so that the color andbrightness of the object vary, the integral tracking unit 200 may addinformation that describes the way the appearance of the object variesin accordance with the position of the object, to the trackinginformation.

For example, if the way the illumination is cast on an object varies inaccordance with the position of the object, the integral tracking unit200 may predict the way the illumination is cast determining from theposition of the object, and may add information, which describes the waythe object is brightened, darkened, or its color changes, to thetracking information for the corresponding tracker.

For example, if the position of an illumination in a space where anobject is disposed is known, the integral tracking unit 200 maydetermine whether or not the shadows of the other objects or the shadowsof all other things disposed in this environment overlap the objectusing the relation between the illumination and the object. If there isa possibility that these shadows overlap the object, the integraltracking unit 200 may calculate overlapping possibility related to theobject that are overlapped by any of these shadows, and may add theoverlapping possibility to the corresponding tracking information.

In some embodiments, even if an illumination is moving such as the sun,the integral tracking unit 200 may obtain the position of the sundetermining from information related to the time and the direction ofthe sun from the site (e.g., the position of the corresponding camera20), predict a direction in which a shadow is made, and take theinfluence of the shadow exerted on the appearance of the object intoconsideration. For example, the integral tracking unit 200 may obtainthe current position of the sun from the time information, and estimatethe direction in which a shadow is made with reference to the currentposition of the sun as well as the information related to the directionof the sun from the site. In some embodiments, if there is a possibilitythat the shadows of the other objects overlap, the integral trackingunit 200 may calculate the possibility (likelihood) of overlapping ofthe object and the shadows of the other objects, and add the possibilityto the tracking information.

The operation of a detection unit 100 will be described. As is the casewith the detection units of the above-described exemplary embodiments,the detection unit 100 may detect objects on the basis of the trackinginformation. In this case, the detection unit 100 of the object trackingapparatus 10 according to the present exemplary embodiment may controlthe detection of objects using information related to the appearances ofthe respective objects included in the tracking information. In someembodiments, the detection unit 100 may not perform detection on anobject likely to be unviewable owing to the overlapping of otherobjects. For example, the detection unit 100 may not set a searchingarea for this object likely to be unviewable.

If information related to the changes of brightness and color isincluded in the tracking information, the detection unit 100 may performdetection after correcting the effect of the corresponding illuminationin searching. For example, in a dark area, the detection unit 100 mayperform detection after setting the pixel values in the area brighter.

In a case where the color of an object changes, when the detection unit100 updates a matching parameter used for template matching (e.g., oneof the above-described detection parameters), the detection unit 100 maycorrect color information included in the parameter taking the change ofthe color into consideration. If the color of an object greatly changes,the detection unit 100 may not use the color information. In someembodiments, the detection unit 100 may lower the weight of the colorinformation and raise the weights of other features such as an edgeamong the features of the template.

When the detection parameters used for object detection processing isupdated by the detection unit 100, if it is determined there is a highpossibility that the object is overlapped, the detection unit 100 maynot update the detection parameter.

As described above, the detection unit 100 may control the detection ofan object on the basis of the appearance information included in thetracking information. As described above, the detection unit 100 canomit the detection processing of an unviewable object and the updateprocessing of parameters for template matching and the like. This canreduce a possibility that the detection unit 100 performs erroneousdetection or an erroneous update of the parameters.

In a similar way, if there is a high possibility that an illuminationcondition changes, the detection unit 100 can control so that theparameters are updated after the effect of the illumination iscorrected, or the parameters are not updated.

If a detection unit 100 is configured to be able to switch detectionalgorithms (e.g., detecting an entire head, detecting a part of thehead, etc.) as described below, the object tracking apparatus 10 may usea detector having more robustness to the overlappings of objects as thedetection unit 100. In some embodiments, the object tracking apparatus10 may use a detector that detects an entire head. In some embodiments,in a case where there is an overlapping, the object tracking apparatus10 may use a detector that detects a part of the head. In such a way,the object tracking apparatus 10 may usually use a simple detector, andif there is a possibility of an overlapping, the object trackingapparatus 10 can use a more elaborate detector. Therefore, the objecttracking apparatus 10 can perform more precise detection whilemaintaining efficiency. In a similar way, if an illumination conditionchanges, the object tracking apparatus 10 can control detection using adetector whose robustness against the illumination condition is high (afeature).

As described above, in the object tracking apparatus 10 according to thepresent exemplary embodiment, the integral tracking unit 200 maydetermine the appearance of an object using not only information fromthe corresponding camera but also information from other cameras.Therefore, even in a case where a certain camera 20 cannot make acorrect determination such as a case where objects overlap each otherwhen viewed from the certain camera 20, the integral tracking unit 200may determine more precisely the appearances of the respective objects.The integral tracking unit 200 may provide this result to the detectionunit 100. This can reduce a possibility that the detection unit 100performs erroneous detection. Because the integral tracking unit 200performs object tracking using this result, the precision of the objecttracking can be improved.

In the above exemplary embodiments, descriptions have been made underthe assumption that the object tracking apparatus 10 includes detectionunits (100 or 400) and the integral tracking unit (200 or 500). In someembodiments, these detection units and integral tracking unit may berealized in respective separate devices. In other aspects, the detectionunits (100 or 400) may be realized as object detection devices byseparate devices, and the integral tracking unit (200 or 500) may berealized as an integral tracking device by a separate device. In otheraspects, the display control unit 300 may be realized as a separatedisplay control device independently of the object tracking apparatus50. In other aspects, this display control device may be embedded in thedisplay device 30.

<Example of Hardware Configuration>

An example of hardware configuration that may realize the objecttracking apparatus (10 or 50) according to any of the above-describedexemplary embodiments will be described. The above-described objecttracking apparatus (10 or 50) may be realized by a dedicated apparatusor by a computer (information processing apparatus).

FIG. 19 is a diagram for illustrating the hardware configuration of acomputer (information processing apparatus) capable of realizingrespective exemplary embodiments.

The hardware of an information processing apparatus (computer) 700 mayinclude a CPU (central processing unit) 11, a communication interface(I/F) 12, an input/output user interface 13, a ROM (read only memory)14, a RAM (random access memory) 15, a memory device 17 and a drivedevice 18 for a computer-readable memory medium 19, and these componentsmay be coupled with one another via a bus 16. The input/output userinterface 13 may be a man-machine interface such as a keyboard, which isan example of an input device, a display, which is an example of anoutput device, or the like. The communication interface 12 may be atypical communication means used for the apparatus according to any ofthe above-described exemplary embodiments (illustrated in FIG. 1 or FIG.9) to communicate with external apparatuses via a communication network600. In the above hardware configuration, the CPU 11 may control theentire motion of the information processing apparatus 700 that realizesthe object tracking apparatus (10 or 50) according to any of theabove-described exemplary embodiments.

After a program (computer program) that can realize processing describedin the above-described respective exemplary embodiments is provided tothe information processing apparatus 700 illustrated in FIG. 19, thepresent disclosure, which has been described in the forms of theabove-described exemplary embodiments, is realized by making the CPU 11execute the program. Such a program as above may be a program that iscapable of realizing various processes described in the flowchart (FIG.8), which is referred to in the explanations of the above-describedrespective exemplary embodiments, or that is capable of realizing therespective units (blocks) in the corresponding devices illustrated inthe block diagrams in FIG. 1, FIG. 4 to FIG. 6, FIG. 9, and FIG. 15 toFIG. 17.

The program provided to the information processing apparatus 700 may bestored in a temporary read/write memory (15) or in a nonvolatile memorydevice (17) such as a hard disk drive. In some embodiments, in thememory device 17, a program group 17A may include, for example, programsthat can realize the functions of the respective units illustrated inthe object tracking apparatus (10 or 50) according to any of theabove-described respective examples and embodiments. In someembodiments, various kinds of stored information 17B may be, forexample, object tracking results in the above-described respectiveexemplary embodiments, camera videos, camera parameters, areas ofcoordinate values in the common coordinate system that are viewable torespective cameras 20, and the like. In some embodiments, in theinstallation of the programs in the information processing apparatus700, the configuration units of respective program modules are belimited to the segments corresponding to respective blocks illustratedin the block diagrams (in FIG. 1, FIG. 4 to FIG. 6, FIG. 9, and FIG. 15to FIG. 17), and those skilled in the art can appropriately select asegmentation method of the programs in their installation of theprograms.

In the above-described case, many typical procedures may be adoptednowadays as a provision method of the programs to the above apparatussuch as a method in which the programs are installed to the aboveapparatus via a computer readable various media (19) such as a CD(compact disk)-ROM, or a flash memory, and a method in which theprograms are downloaded via a communication line (600) such as theInternet. In this case, the present disclosure may include codes thatforms such programs as above (program group 17A), or the memory medium(19) that stores such codes.

The present disclosure has been described as an example which is appliedto the above-described typical exemplary embodiments. The technologicalscope, however, is not limited to the scope described in the aboverespective exemplary embodiments. It will be obvious to those skilled inthe art that various variations and modifications may be made in theabove respective exemplary embodiments. Even in a case where suchvariations and modifications are added to the above exemplaryembodiments, it can be said that a new exemplary embodiment falls withinthe technological scope. This is obvious from items described in theaccompanying claims.

1. An object tracking apparatus, comprising: a memory storinginstructions; and at least one processor configured to process theinstructions to: generate a first detection result of an object fromoutput information of a first sensor; generate a second detection resultof the object from output information of a second sensor; generate firsttracking information of the object based on a combination of the firstand second detection results, wherein the first tracking information isrepresented in a common coordinate system that is associated with thefirst and the second sensor; and track the object based on the firsttracking information.
 2. The object tracking apparatus according toclaim 1, wherein the at least one processor is configured to process theinstructions to detect the object from videos output from the sensors.3. The object tracking apparatus according to claim 1, wherein the atleast one processor is configured to process the instructions to:generate second tracking information of the object, wherein the secondtracking information is represented in an individual coordinate systemassociated with one of the first and second sensors; and determine asearching area for searching for the object based on the second trackinginformation; wherein at least one of the first and second detectionresult is updated based on the determined searching area.
 4. The objecttracking apparatus according to claim 3, wherein the at least oneprocessor is configured to process the instructions to display thesearching area on a display device.
 5. The object tracking apparatusaccording to claim 3, wherein the first and second detection results aregenerated based on one or more detection parameters; wherein the one ormore detection parameters are updated based on at least one of the firstand second tracking information; and wherein the first trackinginformation is generated based on a relationship between the first andsecond detection results.
 6. The object tracking apparatus according toclaim 1, wherein the at least one processor is configured to process theinstructions to: calculate a first likelihood that reflects a likelihoodof the object included in at least one of the first and second detectionresults; wherein the object is tracked based on the first likelihood. 7.The object tracking apparatus according to claim 1, wherein the at leastone processor is configured to process the instructions to: calculate asecond likelihood that reflects an accuracy of tracking of pastpositions of the object; wherein the object is tracked based on thesecond likelihood.
 8. The object tracking apparatus according to claim1, wherein the first detection result is generated at a prior time thanthe second detection result; wherein the first detection result andsecond detection result include time information; wherein the at leastone processor is configured to process the instructions to: determinethat the object is included in the first detection result; and associatethe object with the second detection result based on a chronologicalorder of the time information between the first and second detectionresults; and wherein the tracking of the object is based on theassociation.
 9. The object tracking apparatus according to claim 1,wherein the first detection result and second detection result includetime information; wherein the at least one processor is configured toprocess the instructions to: determine that the object is included inthe first detection result; and associate the object with the seconddetection result based on the time information that indicates the firstand second detection results are generated within a predetermined timeperiod; and wherein the tracking of the object is based on theassociation.
 10. The object tracking apparatus according to claim 1,wherein the at least one processor is configured to process theinstructions to: transform the first tracking information represented inthe common coordinate system into the second tracking informationrepresented in the individual coordinate systems associated with,respectively, the first and second sensors; and transform at least oneof first and second detection results represented in the individualcoordinate systems to detection results represented in a commoncoordinate system.
 11. The object tracking apparatus according to claim1, wherein the at least one processor is configured to process theinstructions to: generate information related to appearance of theobject based on at least one of the first and second detection results;and include the information related to appearance of the object into thetracking information; wherein at least one of the first and seconddetection results are updated based on the information related toappearance of the object included in the tracking information.
 12. Theobject tracking apparatus according to claim 1, wherein the informationrelated to appearance of the object includes information that indicatesan overlapping between the object and other objects; and wherein the atleast one processor is configured to process the instructions to:determine the overlapping between the object and the other objects basedon at least one of the first and second detection results; update theinformation related to appearance of the object based on theoverlapping; and wherein at least one of the first and second detectionresults are updated based on the updated information related toappearance of the object included in the tracking information.
 13. Anobject tracking system comprising sensors and an object trackingapparatus, wherein the object tracking apparatus includes: a memorystoring instructions; and at least one processor configured to processthe instructions to: generate a first detection result of an object fromoutput information of a first sensor; generate a second detection resultof the object from output information of a second sensor; generate firsttracking information of the object based on a combination of the firstand second detection results, wherein the first tracking information isrepresented in a common coordinate system that is associated with thefirst and the second sensor; and track the object based on the firsttracking information.
 14. An object tracking method comprising:generating, by a processor, a first detection result of an object fromoutput information of a first sensor; generating, by a processor, asecond detection result of the object from output information of asecond sensor; generating, by a processor, first tracking information ofthe object based on a combination of the first and second detectionresults, wherein the first tracking information is represented in acommon coordinate system that is associated with the first and thesecond sensor; and tracking, by a processor, the object based on thefirst tracking information.
 15. An object detection device, comprising:a memory storing instructions; and at least one processor configured toprocess the instructions to: detect an object from output information ofsensors on a basis of tracking information represented in a commoncoordinate system, and wherein the tracking information indicatingtracking result of the object tracked on a basis of a plurality ofdetection results output from individuals of a plurality of objectdetection devices.
 16. A non-transitory computer-readable storage mediummay store instructions that when executed by a computer enable thecomputer to implement a method comprising: generating a first detectionresult of an object from output information of a first sensor;generating a second detection result of the object from outputinformation of a second sensor; generating first tracking information ofthe object based on a combination of the first and second detectionresults, wherein the first tracking information is represented in acommon coordinate system that is associated with the first and thesecond sensor; and tracking the object based on the first trackinginformation.